arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1707.04404cond-mat.stat-mech
收藏

驻波和驻波磁场驱动下自旋S Ising铁磁体的非平衡相变

Nonequilibrium phase transition in spin-S Ising ferromagnet driven by Propagating and Standing magnetic field wave

Ajay Halder, Muktish Acharyya

摘要:

采用扩展的蒙特卡罗模拟,在二维空间中研究了自旋S(S=1,3/2,2,3)Ising铁磁体对平面传播波、驻波磁场和恒定频率均匀振荡场的动力学响应.根据磁场的强度和伊辛自旋晶格的自旋态的值,观察到两个不同的动力学相。对于固定的S值和传播磁场波的振幅,随着系统温度的降低,系统经历从传播相到钉扎相的动态相变。类似地,在驻波磁波的情况下,系统经历从高温相到低温钉扎或自旋冻结相的动态相变,在高温相,自旋在驻波磁波的半波长的交替带中相干振荡。当磁场振荡幅度一定时,随着自旋S的增加,相变温度降低到一个极限值。在磁场振荡的整个周期上的时间平均磁化强度起到动态序参量的作用。在磁场幅值和动态相变温度的平面上画出了一个综合相界。发现当自旋态S值较高时,相界向内收缩。在低温(和高场)区域中,相边界也是紧密间隔的。

英文摘要:

The dynamical response of spin-S (S=1, 3/2, 2, 3) Ising ferromagnet to the plane propagating wave , standing magnetic field wave and uniformly oscillating field with constant frequency are studied separately in two dimensions by extensive Monte Carlo simulation. Depending upon the strength of the magnetic field and the value of the spin state of the Ising spin lattice two different dynamical phases are observed. For a fixed value of S and the amplitude of the propagating magnetic field wave the system undergoes a dynamical phase transition from propagating phase to pinned phase as the temperature of the system is cooled down. Similarly in case with standing magnetic wave the system undergoes dynamical phase transition from high temperature phase where spins oscillates coherently in alternate bands of half wavelength of the standing magnetic wave to the low temperature pinned or spin frozen phase. For a fixed value of the amplitude of magnetic field oscillation the transition temperature is observed to decrease to a limiting value as the value of spin S is increased. The time averaged magnetisation over a full cycle of the magnetic field oscillation plays the role of the dynamic order parameter. A comprehensive phase boundary is drawn in the plane of magnetic field amplitude and dynamic transition temperature. It is found that the phase boundary shrinks inwards for high value of spin state S. Also in the low temperature (and high field) region the phase boundaries are closely spaced.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑