@article{ranautFrustratedGarnetGd3Te2Li3O122026,

title = {Frustrated Garnet Gd_{3}Te_{2}Li_{3}O_{12} for High-Performance Sub-Kelvin Adiabatic Demagnetization Refrigeration},

author = {D. Ranaut and G. Unnikrishnan and Samraj M and S. K. Channarayappa and P. K. Mukharjee and P. Saravanan and P. Gegenwart and D. Jaiswal-Nagar},

url = {https://doi.org/10.1021/acsaelm.6c01619},

doi = {10.1021/acsaelm.6c01619},

issn = {2637-6113},

year  = {2026},

date = {2026-10-22},

urldate = {2026-10-01},

journal = {ACS Appl. Electron. Mater.},

abstract = {Owing to the limited availability and high cost of 3He, adiabatic demagnetization refrigeration (ADR) has gained considerable attention as an efficient technology for ultralow-temperature applications. Here, we demonstrate the frustrated garnet Gd3Te2Li3O12 (GTLG) as a high-performance ADR material with substantially improved cooling capability over the commercial benchmark Gd3Ga5O12 (GGG). Direct ADR measurements reveal a minimum temperature of 165 mK for GTLG, nearly two-fold lower than that of GGG (320 mK). Under a cryostat bath temperature of 1.8 K, GTLG maintains temperatures below 1 K for more than 12 h and below the 3He-temperature (0.4 K) for over 3 h, demonstrating excellent temperature stability for prolonged cryogenic operation. Magnetic and thermodynamic measurements show that GTLG undergoes antiferromagnetic ordering at TN ∼ 0.25 K while retaining strong magnetic frustration and a large magnetic entropy reservoir favorable for efficient demagnetization cooling. Field-dependent heat capacity and magnetic Grüneisen parameter measurements further reveal the presence of field-induced critical behavior that enables cooling below TN through enhanced entropy accumulation near the critical region. These findings establish GTLG as a promising next-generation magnetic refrigerant and highlight field-induced criticality as an effective design principle for developing advanced materials for ultralow-temperature refrigeration.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{jawaleLowtemperatureMagnetismSpin2026,

title = {Low-temperature magnetism and spin dynamics in the disordered triangular-lattice Yb^{3+} compound LiCaYb_{5}(BO_{3})_{6}},

author = {M. Jawale and S. Nandi and P. K. Mukharjee and P. Gegenwart and A. V. Mahajan},

url = {https://link.aps.org/doi/10.1103/px8x-fcqp},

doi = {10.1103/px8x-fcqp},

year  = {2026},

date = {2026-09-25},

urldate = {2026-09-01},

journal = {Phys. Rev. B},

volume = {114},

number = {16},

pages = {165140},

publisher = {American Physical Society},

abstract = {The interplay between geometric frustration, spin-orbit coupling, and structural disorder can give rise to unconventional magnetic ground states in rare-earth triangular-lattice magnets. We report low-temperature magnetic and 7Li NMR investigations of the disordered triangular-lattice compound LiCaYb5(BO3)6 (LCYBO). Rietveld refinement confirms a hexagonal 𝑃⁢65⁢22 structure with partial Ca/Yb antisite disorder and fractional Li occupancy. Magnetic susceptibility and magnetization measurements indicate a well-isolated effective 𝐽eff=1/2 Kramers doublet with weak antiferromagnetic interactions (𝜃CW≈−0.54K). The specific heat reveals a weak anomaly near 0.43 K, suggesting the development of short-range correlated magnetism rather than conventional long-range order. 7Li NMR spectra broaden strongly upon cooling, consistent with increasingly inhomogeneous internal magnetic fields. The spin-lattice relaxation exhibits two relaxation components consistent with disorder-induced distributions of local magnetic environments arising from antisite disorder and competing exchange pathways. Our results establish LCYBO as a structurally disordered frustrated triangular-lattice magnet with correlated low-energy spin dynamics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{xn3r-b7g6,

title = {Magnetic symmetry and hyperfine fields of V_4 tetrahedral clusters in the multiferroic lacunar spinel GeV_{4}S_{8}},

author = {T. Gimpel and N. Büttgen and L. Prodan and V. Tsurkan and A. A. Tsirlin and H. Nakamura and I. Kézsmárki},

url = {https://link.aps.org/doi/10.1103/xn3r-b7g6},

doi = {10.1103/xn3r-b7g6},

year  = {2026},

date = {2026-09-18},

urldate = {2026-09-01},

journal = {Phys. Rev. B},

volume = {114},

number = {15},

pages = {154418},

abstract = {We use 51V nuclear magnetic resonance (NMR) spectroscopy to investigate the magnetic ground state of the lacunar spinel GeV4⁢S8, which undergoes a structural distortion at 𝑇JT≈30K followed by an antiferromagnetic (AFM) ordering at 𝑇𝑁≈15K. According to our zero- and finite-field NMR data, the four V-sites of V4 clusters become magnetically inequivalent in the AFM state: Two of them share the same internal field, while the other two sites are characterized by different internal fields. The angular dependence of the 51V NMR lines, upon rotation of an external magnetic field about the pseudocubic [110] and [100] axes, reveals that the internal fields are either parallel to the orthorhombic 𝑎 axis at all four V-sites of the V4 tetrahedra, or they form an orthogonal pattern, where two V-sites have internal field along the 𝑎 axis and the other two along the 𝑏 axis. Based on these results, further supported by the observation of distinct spin-echo modulations of the inequivalent V-sites, we conclude that the magnetic space group of the AFM state is 𝑃𝑏⁢𝑚⁢𝑛⁢21 or 𝑃⁢𝑚⁢𝑛′⁢2′1.},

note = {datadoi: (10.5281/zenodo.20604906)},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{xcr2-rxv6,

title = {Dynamic spin fluctuations in the S = ⁵⁄₂ tetratrillium lattice antiferromagnet KBaFe_{2}(PO_{4})_{3}},

author = {S. J. Sebastian and S. S. Islam and R. Kolay and S. Mohanty and Q. -P. Ding and Y. Skourski and J. Sichelschmidt and M. Baenitz and J. A. Krieger and T. J. Hicken and H. Luetkens and A. A. Tsirlin and Y. Furukawa and R. Nath},

url = {https://link.aps.org/doi/10.1103/xcr2-rxv6},

doi = {10.1103/xcr2-rxv6},

year  = {2026},

date = {2026-08-11},

urldate = {2026-08-01},

journal = {Phys. Rev. B},

volume = {114},

number = {8},

pages = {L080403},

abstract = {The three-dimensional (3D) magnet KBaFe2(PO4)3 hosts an effective tetratrillium spin lattice of Fe3+ (𝑆=5/2) ions, offering a prototypical platform to study frustration-driven phenomena in 3D. Through magnetization, specific heat, 31P nuclear magnetic resonance (NMR), and muon spin relaxation (µ⁢SR) experiments, supported by first-principles calculations, we uncover an unconventional ground state. Despite strong antiferromagnetic interactions with a large Curie-Weiss temperature 𝜃CW=−70⁢(2)⁢K, no magnetic long-range order is observed down to 30 mK. Below 𝑇*≃3.5K, the NMR linewidth becomes nearly field independent and the spin-spin relaxation rate 1/𝑇2 saturates, accompanied by a two-component relaxation in the transverse nuclear magnetization 𝑀𝑥⁢𝑦. The latter indicates the emergence of short-range dynamical correlations, which was further corroborated by a robust and field-insensitive broad maximum in specific heat. In µ⁢SR, we detect neither a static internal field nor spin freezing; instead, the spins remain dynamic down to 30 mK and the asymmetry curves are best described by two coexisting dynamic relaxation channels: a dominant fast (sporadic) channel and a slower Markovian component. Their differing weights and fluctuation rates suggest microscopic inhomogeneity in spin dynamics. These persistent low-temperature spin fluctuations are found to be intrinsic to the 3D frustrated tetratrillium geometry, exemplifying KBaFe2(PO4)3, a rare 3D antiferromagnet with a classical spin that fosters unconventional dynamics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{opletalComplexMagneticBehavior2026,

title = {Complex magnetic behavior of the Ce sawtooth chains in CeRhSn_{2}},

author = {P. Opletal and J. Fikáček and E. Duverger–Nédellec and A. Thamizhavel and Z. Hossain and R. Tarasenko and V. Tkáč and D. Legut and Bin Shen and P. Gegenwart and J. Custers},

url = {https://link.aps.org/doi/10.1103/pkdg-n4yk},

doi = {10.1103/pkdg-n4yk},

year  = {2026},

date = {2026-07-17},

urldate = {2026-07-01},

journal = {Phys. Rev. B},

volume = {114},

number = {4},

pages = {045118},

publisher = {American Physical Society},

abstract = {Conflicting reports exist on the ground state of the intermetallic compound CeRhSn2. This can be rooted in the sawtoothlike arrangement of two inequivalent Ce sites in the unit cell, which suggests potential geometric magnetic frustration. To resolve these conflicting reports, we conducted a comprehensive study on high-quality single crystals of CeRhSn2 by means of magnetization (𝑀), specific heat (𝐶p/𝑇), and resistivity (𝜌). The system exhibits strong magnetic anisotropy, confirming the 𝑏 axis as the easy magnetic axis. We establish three successive transitions: an antiferromagnetic order at 𝑇N=3.65K, a first-order ferromagnetic (FM) order at 𝑇C=1.7K and final transition, at 𝑇=1.5K. The transition temperatures are highly field-directional dependent: in a magnetic field, the lowest transition is immediately suppressed while 𝐇∥𝑏 rapidly merges 𝑇C and 𝑇N into a single second-order transition. Conversely, 𝐇∥𝑐 suppresses the FM order and reduces 𝑇N. Additional ab initio calculations affirm the FM ground state of CeRhSn2. The observation of an enhancement of the Sommerfeld coefficient (𝛾=76.5mJ/molK2) may arise from geometric frustration, but it is most consistently attributed to weak Kondo hybridization as frustration cannot be conclusively established through our data.},

note = {datadoi: 10.5281/zenodo.20434110},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{breitner2026magneticelectricpropertiesmetallic,

title = {Magnetic and electric properties of the metallic kagome antiferromagnet CrRhAs},

author = {F. Breitner and B. Shen and A. Jesche and A. A. Tsirlin and P. Gegenwart},

url = {https://link.aps.org/doi/10.1103/d449-1tfw},

doi = {10.1103/d449-1tfw},

year  = {2026},

date = {2026-06-30},

urldate = {2026-06-01},

journal = {Phys. Rev. Mater.},

volume = {10},

number = {6},

pages = {064204},

abstract = {CrRhAs is an antiferromagnetic kagome metal predicted to host a nontrivial spin texture with vector spin chirality [Huang et al., npj Quantum Mater. 8, 32 (2023)]. We report the synthesis and basic characterization of CrRhAs single crystals, which exhibit an antiferromagnetic transition with 𝑇N = 150 K, evidenced by electrical transport, heat capacity, and magnetization measurements. Hall resistivity varies linearly with magnetic field, i.e., there is no nonlinear Hall contribution. Intriguingly, the Hall coefficient changes sign between the configurations of 𝑗∥𝑎⁢𝑏, 𝐻⁡⊥⁢𝑎⁢𝑏 and 𝑗∥𝑐, 𝐻⁡⊥⁢𝑐, which is likely connected to a peculiar topology of the Fermi surface. Furthermore, for 𝑗∥𝑎⁢𝑏, the Hall coefficient shows a pronounced and continuous enhancement below 𝑇N, signaling a significant reconstruction of the Fermi surface or an extra scattering from the magnons. Our results offer guidance for exploring anomalous electrical transport phenomena in exotic magnetic systems.},

note = {datadoi: 10.5281/zenodo.19046826},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{xl5f-zj9p,

title = {Three-dimensional XY universality and nonlinear magnetic susceptibility in a kagome ice compound},

author = {K. Zhao and H. Deng and H. Chen and N. Ma and N. Oefele and J. Guo and X. Cui and C. Tang and M. J. Gutmann and T. Mueller and Y. Su and V. Hutanu and C. Jin and P. Gegenwart},

url = {https://link.aps.org/doi/10.1103/xl5f-zj9p},

doi = {10.1103/xl5f-zj9p},

year  = {2026},

date = {2026-05-26},

urldate = {2026-05-01},

journal = {Phys. Rev. X},

volume = {16},

number = {2},

pages = {021043},

abstract = {Kagome spin ice is an intriguing class of spin systems constituted by in-plane Ising spins with ferromagnetic interaction residing on the kagome lattice, theoretically predicted to host a plethora of magnetic transitions and excitations. In particular, different variants of kagome spin ice models can exhibit different sequences of symmetry breaking upon cooling from the paramagnetic to the fully ordered ground state. Recently, it has been demonstrated that the frustrated intermetallic HoAgGe stands as a faithful solid-state realization of kagome spin ice. However, whether any of the established symmetry-breaking pathways apply to this material remains unaddressed. Here, we use single-crystal neutron diffuse scattering to map the spin ordering of HoAgGe at various temperatures more accurately; surprisingly, we find that the ordering sequence appears to be different from previously known scenarios: From the paramagnetic state, the system first enters a partially ordered state with fluctuating magnetic charges, in contrast to a charge-ordered paramagnetic phase, before reaching the fully ordered state. Through Monte Carlo simulations and scaling analyses using an extended three-dimensional (3D) spin model for the distorted kagome spin ice in HoAgGe, we elucidate a single 3D XY phase transition into the ground state with broken time-reversal symmetry (TRS). However, the 3D XY transition has a long crossover tail before the fluctuating magnetic charges fully order. More interestingly, we find, both experimentally and theoretically, that the TRS-breaking phase of HoAgGe features an unusual, hysteretic response: Despite their vanishing magnetization, the two time-reversal partners are distinguished and selected by a nonlinear magnetic susceptibility tied to the kagome ice rule. Our discovery not only unveils a new symmetry-breaking hierarchy of kagome spin ice but also demonstrates the potential of TRS-breaking frustrated spin systems for information technology applications.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ynnr-dm9r,

title = {Magnetic transitions in the spin-5/2 triangular lattice antiferromagnet Ba_{3}MnTa_{2}O_{9}},

author = {S. P. Patra and S. Mohanty and S. Samanta and J. K. Oommen and A. A. Tsirlin and R. Nath},

url = {https://link.aps.org/doi/10.1103/ynnr-dm9r},

doi = {10.1103/ynnr-dm9r},

year  = {2026},

date = {2026-04-28},

urldate = {2026-04-28},

journal = {Phys. Rev. B},

volume = {113},

number = {14},

pages = {144436},

publisher = {American Physical Society},

abstract = {We report a comprehensive study of the structural and magnetic properties of the two-dimensional 𝑆=5/2 frustrated triangular-lattice antiferromagnet Ba3⁢MnTa2⁢O9 using x-ray diffraction, magnetization, electron spin resonance, and heat-capacity measurements on a polycrystalline sample, combined with density-functional band-structure calculations. The magnetic susceptibility and heat-capacity data reveal the onset of antiferromagnetic long-range order at 𝑇N≃2.6K, which is in sharp contrast with the recent report by Mondal et al. [Phys. Rev. B 112, 155153 (2025)] who did not observe magnetic order in this material. The nearest-neighbor exchange coupling 𝐽/𝑘B≃0.85K is obtained from Monte Carlo fits to the experimental susceptibility data. Combined with the ab initio estimate of the interlayer coupling, this 𝐽/𝑘B value leads to 𝑇N≃2.7K in a perfect agreement with the experiment. Magnetic isotherms reveal a field-induced transition below 𝑇N. The complex 𝐻−𝑇 phase diagram features multiple phases as a consequence of magnetic frustration and anisotropy present in the system.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{ranautCrystalFieldScheme2026,

title = {Crystal field scheme and field-induced critical behavior in effective spin-1/2 NdVO_{4}},

author = {D. Ranaut and D. T. Adroja and M. Aouane and P. K. Mukharjee and P. Gegenwart and D. Jaiswal-Nagar},

url = {https://link.aps.org/doi/10.1103/c6v8-vx4h},

doi = {10.1103/c6v8-vx4h},

year  = {2026},

date = {2026-04-07},

urldate = {2026-04-04},

journal = {Phys. Rev. B},

volume = {113},

number = {14},

pages = {144411},

publisher = {American Physical Society},

abstract = {Quantum fluctuations in low-spin (𝑆=1/2) systems make them potential materials to investigate various intriguing field-induced quantum phenomena. In this context, rare-earth (4⁢𝑓)-based effective spin (𝐽eff=1/2) systems with localized magnetic moments and low energy scales offer an advantage of low critical fields and provide access to probe the complete magnetic phase diagram. Here, we present inelastic neutron scattering (INS) data to understand the crystal field (CF) scheme of the previously established 𝐽eff=1/2 antiferromagnet NdVO4, along with low-temperature magnetization and heat capacity measurements to construct the complete magnetic phase diagram. Our INS data validate the presence of the 𝐽eff=1/2 state at low temperatures with the ground and first excited CF state separated by an energy of 140 K. Furthermore, it yields a unique CF scheme where the excitation corresponding to the highest (fourth) CF state is observed via transitions involving the first and second excited states. Magnetic and heat capacity measurements yield the presence of a field-induced first-order spin-flop transition within the second-order antiferromagnetic (AFM) state. Magnetic phase diagrams constructed using the field-dependent magnetization and magnetic heat capacity reveal a continuous transformation from AFM to spin-flop state with a critical field of 𝐻sf∼1.4T. The presence of quantum fluctuations near 𝐻sf are evident from the V-shaped region in entropy contours indicating the presence of accumulated entropy.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kuchlerHighresolutionCapacitanceDilatometry2026,

title = {High-resolution capacitance dilatometry of microscopically thin samples using a miniature dilatometer},

author = {R. Küchler and S. N. Panja and S. Wirth and P. Gegenwart},

url = {https://doi.org/10.1063/5.0300507},

doi = {10.1063/5.0300507},

issn = {0034-6748},

year  = {2026},

date = {2026-02-12},

urldate = {2026-02-01},

journal = {Rev. Sci. Instrum.},

volume = {97},

number = {2},

pages = {025209},

abstract = {We present a novel application of our high-resolution capacitance dilatometer, specifically engineered for the precise characterization of quantum materials. These materials, which often appear as ultrathin, platelet-shaped crystals, are known for exotic phenomena such as superconductivity, topological order, and quantum spin liquid. However, these crystals seldom reach macroscopic dimensions, making them unsuitable for conventional dilatometry techniques. By introducing a modified sample-mounting configuration, our design enables high-resolution measurements of thermal expansion and magnetostriction along in-plane crystallographic directions in samples with thicknesses well below 500 μm. Validation measurements using a Quantum Design PPMS system confirm reliable performance for a 300 μm-thick silver platelet, relatively hard ferromagnetic EuB6 single crystals down to 50 μm, and a 40 μm-thin, soft AgCrS2 single crystal. This advancement significantly broadens the applicability of capacitance dilatometry, providing a powerful platform for investigating emergent phenomena in reduced-dimensional quantum systems.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{magarProximateSpinliquidBehavior2025,

title = {Proximate spin-liquid behavior in the double trillium lattice antiferromagnet K_{2}Co_{2}(SO_{4})_{3}},

author = {A. Magar and K. Somesh and M. P. Saravanan and J. Sichelschmidt and Y. Skourski and M. T. F. Telling and V. A. Ginga and A. A. Tsirlin and R. Nath},

url = {https://doi.org/10.1103/m8mj-slvl},

doi = {10.1103/m8mj-slvl},

year  = {2026},

date = {2026-01-16},

urldate = {2026-01-01},

journal = {Phys. Rev. B},

volume = {113},

number = {2},

pages = {L020409},

abstract = {We report proximate quantum spin liquid behavior in K2⁢Co2 (SO4)3 with the magnetic Co2+ ions embedded on a highly frustrated three-dimensional double trillium lattice. Single-crystal and high-resolution synchrotron powder x-ray diffraction experiments reveal a structural phase transition at 𝑇_t≃125K from high-temperature cubic to low-temperature monoclinic phase with the threefold superstructure. Magnetization and heat capacity consistently show the formation of the 𝐽eff=1/2 state of Co2+ below 50 K. In zero field, K2⁢Co2(SO4)3 shows signatures of static magnetic order formed below 𝑇*≃0.6K, but muon spin relaxation experiments reveal a large fluctuating component that persists down to at least 50 mK, reminiscent of quantum spin liquid (QSL). Static order is completely suppressed in the small magnetic field of ∼1T, and low-temperature heat capacity demonstrates the 𝑇2 behavior above this field, another fingerprint of QSL. Ab initio calculations show a competition of several antiferromagnetic couplings that render K2⁢Co2(SO4)3 a promising pseudospin-1/2 material for studying quantum magnetism in the double trillium lattice geometry.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{klingerSub1AdiabaticDemagnetization2026,

title = {Sub-1 K Adiabatic Demagnetization Refrigeration with Rare-Earth Borates Ba_{3}XB_{9}O_{18} and Ba_{3}XB_{3}O_{9}, X = (Yb, Gd)},

author = {M. Klinger and T. Treu and F. Kreisberger and C. Heil and A. Klinger and A. Jesche and P. Gegenwart},

url = {https://doi.org/10.3390/app16010290},

doi = {10.3390/app16010290},

year  = {2025},

date = {2025-12-27},

urldate = {2026-01-01},

journal = {Appl. Sci.},

volume = {16},

number = {1},

pages = {290},

abstract = {Adiabatic demagnetization refrigeration (ADR) is regaining relevance for refrigeration to temperatures below 1 K as global helium-3 supply is increasingly strained. While ADR at these temperatures is long established with paramagnetic hydrated salts, more recently, frustrated rare-earth oxides were found to offer higher entropy densities and practical advantages, since they do not degrade under heating or evacuation. We report structural, magnetic, and thermodynamic properties of the rare-earth borates Ba3XB9O18 and Ba3XB3O9 with X = (Yb, Gd). Except for Ba3GdB9O18, which orders at 108 mK, the three other materials remain paramagnetic down to their lowest measured temperatures. ADR performance starting at 2 K in a field of 5 T is analyzed and compared to literature.},

note = {datadoi: 10.5281/zenodo.17855051},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{wang_antiferromagnetic_2025,

title = {Antiferromagnetic ordering and critical behavior induced giant magnetocaloric effect in distorted kagome lattice Gd_{3}BWO_{9}},

author = {Z. Wang and X. Cui and T. Treu and J. Guo and X. Liu and M. Klinger and C. Heil and N. Ma and X. Sheng and Z. Deng and X. Lu and X. Wang and W. Li and P. Gegenwart and C. Jin and K. Zhao},

url = {https://link.aps.org/doi/10.1103/7l6y-hdw5},

doi = {10.1103/7l6y-hdw5},

year  = {2025},

date = {2025-09-16},

urldate = {2025-09-01},

journal = {Phys. Rev. Mater.},

volume = {9},

number = {9},

pages = {094407},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{telangAdiabaticDemagnetizationRefrigeration2025,

title = {Adiabatic demagnetization refrigeration with antiferromagnetically ordered NaGdP_{2}O_{7}},

author = {P. Telang and T. Treu and M. Klinger and A. A. Tsirlin and P. Gegenwart and A. Jesche},

url = {https://link.aps.org/doi/10.1103/PhysRevB.111.064431},

doi = {10.1103/PhysRevB.111.064431},

year  = {2025},

date = {2025-02-28},

urldate = {2025-02-01},

journal = {Phys. Rev. B},

volume = {111},

number = {6},

pages = {064431},

abstract = {We present a comprehensive study of the structural, magnetic, and thermodynamic properties, as well as the adiabatic demagnetization refrigeration (ADR) performance of NaGdP2⁢O7. Although NaGdP2⁢O7 exhibits antiferromagnetic ordering at a Néel temperature of 𝑇N=570mK in zero field, ADR experiments achieved a minimum temperature of 220 mK starting from 𝑇=2K under an applied magnetic field of 𝜇0⁢𝐻=5T. The warm-up time back to 𝑇=2K exceeds 60 hours with 9 hours below 𝑇=400mK underscoring the potential of NaGdP2⁢O7 as an efficient precooling stage in double-stage ADR systems. We show that the spin lattice of NaGdP2⁢O7 can be seen as a network of ferromagnetic spin chains with antiferromagnetic interchain couplings and also investigate the influence of antiferromagnetic ordering on the magnetic entropy. We find that the temperature dependence of the entropy plays a more dominant role than its magnetic field dependence in the magnetically ordered state.},

note = {datadoi: 10.5281/zenodo.14697906},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{tang_crystal_2024,

title = {Crystal field magnetostriction of spin ice under ultrahigh magnetic fields},

author = {N. Tang and M. Gen and M. Rotter and H. Man and K. Matsuhira and A. Matsuo and K. Kindo and A. Ikeda and Y. Matsuda and P. Gegenwart and S. Nakatsuji and Y. Kohama},

url = {https://link.aps.org/doi/10.1103/PhysRevB.110.214414},

doi = {10.1103/PhysRevB.110.214414},

year  = {2024},

date = {2024-12-09},

urldate = {2024-12-01},

journal = {Phys. Rev. B},

volume = {110},

number = {21},

pages = {214414},

abstract = {We present a comprehensive study of the magnetoelastic properties of the Ising pyrochlore oxide Ho2⁢Ti2⁢O7, known as spin ice, by means of high-field magnetostriction measurements and numerical calculations. When a magnetic field is applied along the crystallographic ⟨111⟩ axis, the longitudinal magnetostriction exhibits a broad maximum in the low-field regime around 30 T, followed by a dramatic lattice contraction due to crystal-field (CF) level crossing at 𝐵cf∼65 T. The transverse magnetostriction exhibits a contrasting behavior, highlighting the anisotropic nature of the CF striction. By applying a magnetic field at varying sweep rates, we identify distinct timescales of spin dynamics that are relevant to monopole formation and annihilation, as well as CF-phonon dynamics. Our mean-field calculations, based on a point-charge model, successfully reproduce the overall magnetostriction behavior, revealing the competition between the exchange striction and CF striction. A signature of the CF level crossing is also observed through adiabatic magnetocaloric-effect measurements, consistent with our magnetostriction data.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{shenStrongEnhancementMagnetic2024,

title = {Strong Enhancement of Magnetic Coercivity Induced by Uniaxial Stress},

author = {B. Shen and F. Breitner and P. Gegenwart and A. Jesche},

doi = {10.1103/PhysRevLett.133.186702},

year  = {2024},

date = {2024-10-28},

urldate = {2024-10-01},

journal = {Phys. Rev. Lett.},

volume = {133},

number = {18},

pages = {186702},

abstract = {The performance of permanent magnets is intricately tied to their magnetic hysteresis loop. In this study, we investigate the heavy-fermion ferromagnet CeAgSb2 through magnetization measurements under uniaxial stress. We observe a 2400% increase in magnetic coercivity with just a modest stress of approximately 1 kbar. This effect persists even after pressure release, attributable to stress-induced defects that efficiently pin domain walls. Other magnetic properties such as ordering temperature and saturation moment exhibit only weak pressure dependencies and display full reversibility. Our findings offer a promising route for increasing coercive field strength and enhancing the energy product in ferromagnetic materials and are potentially applicable to a broad spectrum of commercial or emerging magnetic applications.},

note = {datadoi: 10.5281/zenodo.10972989},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{kumar_optical_2024,

title = {Optical conductivity of the metallic pyrochlore iridate Pr_{2}Ir_{2}O_{7}: Influence of spin-orbit coupling and electronic correlations on the electronic structure},

author = {H. Kumar and M. Köpf and P. Telang and N. Bura and A. Jesche and P. Gegenwart and C. A. Kuntscher},

url = {https://link.aps.org/doi/10.1103/PhysRevB.110.035140},

doi = {10.1103/PhysRevB.110.035140},

year  = {2024},

date = {2024-07-15},

urldate = {2024-07-15},

journal = {Phys. Rev. B},

volume = {110},

number = {3},

pages = {035140},

abstract = {The synergy of strong spin-orbit coupling and electron-electron interactions gives rise to unconventional topological states, such as topological Mott insulator, Weyl semimetal, and quantum spin liquid. In this study, we have grown single crystals of the pyrochlore iridate Pr2⁡Ir2⁢O7 and explored its magnetic, lattice dynamical, and electronic properties. While Raman spectroscopy data reveal six phonon modes confirming the cubic Fd⁢‾3⁢m crystal symmetry, dc magnetic susceptibility data show no anomalies and hence indicate the absence of magnetic phase transitions down to 2 K. Both temperature-dependent electric transport and optical conductivity data reveal the metallic character of Pr2⁡Ir2⁢O7. The optical conductivity spectrum contains a midinfrared absorption band, which becomes more pronounced with decreasing temperature due to spectral weight transfer from high to low energies. The presence of the midinfrared band hints at the importance of correlation physics. The optical response furthermore suggests that Pr2⁡Ir2⁢O7 is close to the Weyl semimetal phase.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{solana-madruga_covo_3_2023,

title = {CoVO_{3} High-Pressure Polymorphs: To Order or Not to Order?},

author = {E. Solana-Madruga and O. Mentre and A. A. Tsirlin and M. Huve and D. Khalyavin and C. Ritter and A. M. Arevalo-Lopez},

doi = {10.1002/advs.202307766},

year  = {2024},

date = {2024-03-06},

urldate = {2023-12-01},

journal = {Adv. Sci.},

volume = {11},

number = {9},

pages = {2307766},

abstract = {Materials properties are determined by their compositions and structures. In ABO(3) oxides different cation orderings lead to mainly perovskite- or corundum like derivatives with exciting physical properties. Sometimes, a material can be stabilized in more than one structural modification, providing a unique opportunity to explore structure-properties relationship. Here, CoVO3 obtained in both ilmenite-(CoVO3-I) and LiNbO3-type (CoVO3-II) polymorphs at moderate (8-12 GPa) and high pressures (22 GPa), respectively are presented. Their distinctive cation distributions affect drastically the magnetic properties as CoVO3-II shows a cluster-glass behavior while CoVO3-I hosts a honeycomb zigzag magnetic structure in the cobalt network. First principles calculations show that the influence of vanadium is crucial for CoVO3-I, although it is previously considered as non-magnetic in a dimerized spin-singlet state. Contrarily, CoVO3-II shows two independent interpenetrating antiferromagnetic Co- and ferromagnetic V-hcp sublattices, which intrinsically frustrate any possible magnetic order. CoVO3-II is also remarkable as the first oxide crystallizing with the LiNbO3-type structure where both metals contain free d electrons. CoVO3 polymorphs pinpoint therefore as well to a much broader phase field of high-pressure A-site Cobaltites.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{zhaoDiscreteDegeneraciesDistinguished2024,

title = {Discrete degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound},

author = {K. Zhao and Y. Tokiwa and H. Chen and P. Gegenwart},

url = {https://doi.org/10.1038/s41567-023-02307-w},

doi = {10.1038/s41567-023-02307-w},

year  = {2024},

date = {2024-01-10},

urldate = {2024-01-01},

journal = {Nat. Phys.},

volume = {20},

pages = {442},

abstract = {In magnetic crystals, despite the explicit breaking of time-reversal symmetry, two equilibrium states related by time reversal are always energetically degenerate. In ferromagnets, this time-reversal degeneracy is reflected in the hysteresis of the magnetic field dependence of the magnetization and, if metallic, in that of the anomalous Hall effect (AHE). Under time-reversal, both these quantities change signs but not their magnitude. Here we show that a time-reversal-like degeneracy appears in the metallic kagome spin ice HoAgGe when magnetic fields are applied parallel to the kagome plane. We find vanishing hysteresis in the field dependence of the magnetization at low temperature, but finite hysteresis in the field-dependent AHE. This suggests the emergence of states with nearly the same energy and net magnetization but different sizes of the AHE and of the longitudinal magnetoresistance. By analysing the experimental data and a minimal tight-binding model, we identify a time-reversal-like operation connecting these near-degenerate states, which is related to the non-trivial distortion of the kagome lattice in HoAgGe. Our work demonstrates the diagnostic power of transport phenomena for identifying hidden symmetries in frustrated spin systems. Transport measurements of the metallic kagome spin ice HoAgGe show that it has an emergent discrete symmetry that is not apparent from measurements of its magnetization.},

note = {datadoi: 10.1038/s41567-023-02307-w},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{baderGeometricalFrustrationIncommensurate2023,

title = {Geometrical frustration and incommensurate magnetic order in Na_{3}RuO_{4} with two triangular motifs},

author = {V. P. Bader and C. Ritter and E. Papke and P. Gegenwart and A. A. Tsirlin},

url = {https://doi.org/10.1103/PhysRevB.108.144424},

doi = {10.1103/PhysRevB.108.144424},

year  = {2023},

date = {2023-10-19},

urldate = {2023-01-01},

journal = {Phys. Rev. B},

volume = {108},

number = {14},

pages = {144424},

abstract = {Incommensurate magnetic order in the spin-3/2 antiferromagnet Na3⁢RuO4 is uncovered by neutron diffraction combined with ab initio calculations. The crystal structure of Na3⁢RuO4 contains two triangular motifs on different length scales. The magnetic Ru5+ ions form a lozenge (diamond) configuration, with tetramers composed of two isosceles triangles. These tetramers are further arranged in layers, such that an effective triangular lattice is formed. The tetramers are nearly antiferromagnetic but frustration between them leads to an incommensurately modulated magnetic structure described by the propagation vector 𝑘=(0.242⁢(1),0,0.313⁢(1)). We show that the long-range Ru-O-O-Ru couplings between the tetramers play a major role in Na3⁢RuO4 and suggest an effective description in terms of the spatially anisotropic triangular lattice if the tetramers are treated as single sites.},

note = {datadoi: 10.5281/zenodo.8226429},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{mohantyDisorderedGroundState2023,

title = {Disordered ground state in the spin-orbit coupled J_{eff} = 1/2 distorted honeycomb magnet BiYbGeO_{5}},

author = {S. Mohanty and S. S. Islam and N. Winterhalter-Stocker and A. Jesche and G. Simutis and Ch Wang and Z. Guguchia and J. Sichelschmidt and M. Baenitz and A. A. Tsirlin and others},

url = {https://doi.org/10.1103/PhysRevB.108.134408},

doi = {10.1103/PhysRevB.108.134408},

year  = {2023},

date = {2023-10-09},

urldate = {2023-01-01},

journal = {Phys. Rev. B},

volume = {108},

number = {13},

pages = {134408},

abstract = {We delineate quantum magnetism in the strongly spin-orbit coupled distorted honeycomb lattice antiferromagnet BiYbGeO5. Our magnetization and heat capacity measurements reveal that its low-temperature behavior is well described by an effective J(eff) = 1/2 Kramers doublet of Yb3+. The ground state is nonmagnetic with a tiny spin gap. Temperature-dependent magnetic susceptibility, magnetization isotherm, and heat capacity can be modeled well assuming isolated spin dimers with anisotropic exchange interactions J(Z) similar or equal to 2.6 K and J(XY) similar or equal to 1.3 K. Heat capacity measurements backed by muon spin relaxation suggest the absence of magnetic long-range order down to at least 80 mK both in zero field and in applied fields. This sets BiYbGeO5 apart from Yb2Si2O7, with its unusual regime of magnon Bose-Einstein condensation, and suggests negligible interdimer couplings, despite only a weak structural deformation of the honeycomb lattice.},

note = {datadoi: 10.5281/zenodo.8406218},

keywords = {},

pubstate = {published},

tppubtype = {article}

}