Tabei S M A, Gingras M J P, Kao Y-J, Stasiak P, Fortin J-Y
Department of Physics and Astronomy, University of Waterloo, Ontario, N2L 3G1, Canada.
Phys Rev Lett. 2006 Dec 8;97(23):237203. doi: 10.1103/PhysRevLett.97.237203. Epub 2006 Dec 7.
The LiHoxY1-xF4 magnetic material in a transverse magnetic field Bx x perpendicular to the Ising spin direction has long been used to study tunable quantum phase transitions in a random disordered system. We show that the Bx-induced magnetization along the x direction, combined with the local random dilution-induced destruction of crystalline symmetries, generates, via the predominant dipolar interactions between Ho3+ ions, random fields along the Ising z direction. This identifies LiHoxY1-xF4 in Bx as a new random field Ising system. The random fields explain the rapid decrease of the critical temperature in the diluted ferromagnetic regime and the smearing of the nonlinear susceptibility at the spin-glass transition with increasing Bx and render the Bx-induced quantum criticality in LiHoxY1-xF4 likely inaccessible.
长期以来，LiHoxY1-xF4磁性材料在垂直于伊辛自旋方向的横向磁场Bx中被用于研究随机无序系统中的可调谐量子相变。我们表明，沿x方向的Bx诱导磁化，与局部随机稀释引起的晶体对称性破坏相结合，通过Ho3+离子之间占主导的偶极相互作用，产生沿伊辛z方向的随机场。这确定了在Bx中的LiHoxY1-xF4为一种新的随机场伊辛系统。这些随机场解释了稀释铁磁区中临界温度的快速下降以及随着Bx增加自旋玻璃转变处非线性磁化率的展宽，并使得LiHoxY1-xF4中Bx诱导的量子临界性可能无法实现。
