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تسجيل مستخدم جديدAnisotropic temperature-field phase diagram of single-crystalline $beta$-Li$_2$IrO$_3$: magnetization, specific heat, and $^7$Li NMR study
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Detailed magnetization, specific heat, and $^7$Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyperhoneycomb Kitaev magnet $beta$-Li$_2$IrO$_3$ are reported. At high temperatures, {cred anisotropy of the magnetization is reflected by the different Curie-Weiss temperatures for different field directions}, in agreement with the combination of a ferromagnetic Kitaev interaction ($K$) and a negative off-diagonal anisotropy ($Gamma$) as two leading terms in the spin Hamiltonian. At low temperatures, magnetic fields applied along $a$ or $c$ have only a weak effect on the system and reduce the Neel temperature from 38 K at 0 T to about 35.5 K at 14 T, with no field-induced transitions observed up to 58 T on a powder sample. In contrast, the field applied along $b$ causes a drastic reduction in the $T_N$ that vanishes around $H_c=2.8$ T giving way to a crossover toward a quantum paramagnetic state. $^7$Li NMR measurements in this field-induced state reveal a gradual line broadening and a continuous evolution of the line shift with temperature, suggesting the development of local magnetic fields. The spin-lattice relaxation rate shows a peak around the crossover temperature 40 K and follows power-law behavior below this temperature.
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We present magnetization measurements on polycrystalline $beta$-Li$_2$IrO$_3$ under hydrostatic pressures up to 3 GPa and construct the temperature-pressure phase diagram of this material. The magnetically ordered phase with $T_{rm{N}}simeq 38$ K bre
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Temperature-pressure phase diagram of the Kitaev hyperhoneycomb iridate $beta$-Li$_2$IrO$_3$ is explored using magnetization, thermal expansion, magnetostriction, and muon spin rotation ($mu$SR) measurements, as well as single-crystal x-ray diffracti
on under pressure and ab initio calculations. The Neel temperature of $beta$-Li$_2$IrO$_3$ increases with the slope of 0.9 K/GPa upon initial compression, but the reduction in the polarization field $H_c$ reflects a growing instability of the incommensurate order. At 1.4 GPa, the ordered state breaks down upon a first-order transition giving way to a new ground state marked by the coexistence of dynamically correlated and frozen spins. This partial freezing in the absence of any conspicuous structural defects may indicate classical nature of the resulting pressure-induced spin liquid, an observation paralleled to the increase in the nearest-neighbor off-diagonal exchange $Gamma$ under pressure.
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