An alternate model for magnetization plateaus in the molecular magnet V15
An alternate model for magnetization plateaus in the molecular magnet V15
复制标题
分子磁体 V15 中磁化平台的替代模型
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
D. Sen
中科院分区：
文献类型：
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作者：
I. Rudra;S. Ramasesha;D. Sen
本文从V_{15}$中15个自旋为1/2的离子的反铁磁海森堡哈密顿量出发，构造了一个包含8个低阶态（自旋为1/2和自旋为3/2）的耦合到声子池的有效自旋哈密顿量.我们数值求解了该系统的含时薛定谔方程，得到了含时磁场中磁化强度与温度的函数关系。随着磁场扫描速率和温度的变化，磁化强度呈现出不寻常的磁滞和平台模式。观察到的平台不是由于量子隧穿，而是热平均的结果。我们的结果与最近的实验观察是一致的。
Starting from an antiferromagnetic Heisenberg Hamiltonian for the 15 spin-1/2 ions in $V_{15}$, we construct an effective spin Hamiltonian involving eight low-lying states (spin-1/2 and spin-3/2) coupled to a phonon bath. We numerically solve the time-dependent Schrodinger equation of this system, and obtain the magnetization as a function of temperature in a time-dependent magnetic field. The magnetization exhibits unusual patterns of hysteresis and plateaus as the field sweep rate and temperature are varied. The observed plateaus are not due to quantum tunnelling but are a result of thermal averaging. Our results are in good agreement with recent experimental observations.