Kundu S, Dey T, Mahajan A V, Büttgen N
Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
J Phys Condens Matter. 2020 Mar 13;32(11):115601. doi: 10.1088/1361-648X/ab58dc. Epub 2019 Nov 19.
We have investigated the structural and magnetic properties of a new cubic spinel LiZnVO (LZVO) through x-ray diffraction, dc and ac susceptibility, magnetic relaxation, aging, memory effect, heat capacity and Li nuclear magnetic resonance (NMR) measurements. A Curie-Weiss fit of the dc susceptibility [Formula: see text]([Formula: see text]) yields a Curie-Weiss temperature [Formula: see text] K. This suggests strong antiferromagnetic (AFM) interactions among the magnetic vanadium ions. The dc and ac susceptibility data indicate the spin-glass behavior below a freezing temperature T [Formula: see text] 3 K. The frequency dependence of the T is characterized by the Vogel-Fulcher law and critical dynamic scaling behavior or power law. From both fitting, we obtained the value of the characteristic angular frequency [Formula: see text] [Formula: see text] 3.56 [Formula: see text] 10 Hz, the dynamic exponent [Formula: see text] [Formula: see text] 2.65, and the critical time constant [Formula: see text] [Formula: see text] 1.82 [Formula: see text] 10 s, which falls in the conventional range for typical cluster spin-glass (CSG) systems. The value of relative shift in freezing temperature [Formula: see text] [Formula: see text] 0.039 supports a CSG ground states. We also found aging phenomena and memory effects in LZVO. The asymmetric response of the magnetic relaxation below T supports the hierarchical model. Heat capacity data show no long-range or short-range ordering down to 2 K. Only about 25% magnetic entropy change [Formula: see text] signifies the presence of strong frustration in the system. The Li NMR spectra show a shift and broadening with decreasing temperature. The spin-lattice and spin-spin relaxation rates show anomalies due to spin freezing around 3 K as the bulk magnetization.
我们通过X射线衍射、直流和交流磁化率、磁弛豫、老化、记忆效应、热容量以及锂核磁共振（NMR）测量，研究了一种新型立方尖晶石LiZnVO（LZVO）的结构和磁性。直流磁化率公式：见正文的居里-外斯拟合得出居里-外斯温度[公式：见正文]K。这表明磁性钒离子之间存在强反铁磁（AFM）相互作用。直流和交流磁化率数据表明，在低于冻结温度T [公式：见正文] 3 K时存在自旋玻璃行为。T的频率依赖性由Vogel-Fulcher定律以及临界动态标度行为或幂律表征。通过这两种拟合，我们得到了特征角频率[公式：见正文][公式：见正文]3.56 [公式：见正文] 10 Hz、动态指数[公式：见正文][公式：见正文]2.65以及临界时间常数[公式：见正文][公式：见正文]1.82 [公式：见正文] 10 s的值，这些值处于典型团簇自旋玻璃（CSG）系统的常规范围内。冻结温度的相对位移值[公式：见正文][公式：见正文]0.039支持CSG基态。我们还在LZVO中发现了老化现象和记忆效应。低于T时磁弛豫的不对称响应支持分层模型。热容量数据表明，在低至2 K时不存在长程或短程有序。仅约25%的磁熵变[公式：见正文]表明系统中存在强烈的阻挫。锂NMR谱显示随着温度降低出现位移和展宽。自旋晶格和自旋-自旋弛豫率由于在3 K左右的自旋冻结而出现异常，这是体磁化的表现。
