Domain-growth kinetics in the geometrically frustrated isosceles triangular Ising spin system

几何受挫等腰三角形伊辛自旋系统中的畴生长动力学

基本信息

批准号：
14540364
负责人：
MITSUDA Setsuo
金额：
$ 2.3万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

We have studied(i)how the power law holds over wide tempetarwe range inAFphase, revealing that the gxnwth exponent n-02 is almost temperature independent and the pie-factor Cis temperature dependent so that C(T)can be fitted to C_0exp(-dE/k_BT)with a kind of activation energy dE/k_B〜10 K and(ii)domain-growth-kineucs in Ferri-magetic phase at H_s=1300 Oe where A'C'-type domain wall is considered to move almost freely and the time evolution of magnetic suscepbblity c' shows power law c'(t)=c'_<eq>+At^n with n〜02.(iii)preserving anomalously low giowdi exponent n〜0.2, anisotropic pinning effect on domain-wall-motion by non-magnetic impunity was clearly observed for the sample with x=0.005. As anisotiopic suppression of domain growth under extemally applied magnetic field in the sample with x=0.00 has been explained, this anisotiopic pinning effect for domain-wail-motion by non-magnetic impurity can be explained by activation energy consideration ; theA/D-type domain wall motion in the b diiection, which is dominated by the stochastic reversal of free magnetic chains due to the isosceles tnangularlauice geomeby of CoNb2O6, is easily disturbed by non-magnetic impurity, while the domain wall motion in the a diiection is not because all sites have finite activation energy.(iiii)only 1% substitution is enough to suppress the domain-growth-kinetics in this system.(In the H_<//c>-T magnetic phase diagram of the sample with x=0.01, as a consequence of suppression of the domain-growth-kinetics, an apparent incommensurate(IC)state, in which thermodynamically equivalent four types of AF domains, A, B, C, D, arrange quasi-regularly along the b axis(likeA/D/C/B/A/D...)with phase shift of π/2, replaces AF state seen in the sample with x=0.00 as low temperature state, maintaining shape of the magnetic phase boundaries.

我们研究了 (i) 幂律如何在 AF 相的宽温度范围内成立，揭示了 gxnwth 指数 n-02 几乎与温度无关，而饼因子 Ci 与温度相关，因此 C(T) 可以拟合为 C_0exp(- dE/k_BT)，具有一种活化能 dE/k_B〜10 K 和 (ii) 铁磁相中的域生长动力学H_s=1300 Oe 其中 A'C' 型磁畴壁被认为几乎自由移动，磁化率 c' 的时间演化呈现幂律 c'(t)=c'_<eq>+At^n with n〜 02.(iii) 保持异常低的 giowdi 指数 n〜0.2，通过非磁性不罚性对磁畴壁运动的各向异性钉扎效应在具有x=0.005 已经解释了在 x=0.00 的样品中外部施加磁场下磁畴生长的各向异性抑制，非磁性杂质对磁畴壁运动的各向异性钉扎效应可以通过考虑活化能来解释； b 方向的 /D 型磁畴壁运动，由等腰三角形导致的自由磁链的随机反转主导CoNb2O6 的几何结构很容易受到非磁性杂质的干扰，而 a 方向上的畴壁运动并不是因为所有位点都具有有限的活化能。（iii）仅 1% 的取代就足以抑制（在 x=0.01 的样品的 H_</c>-T 磁相图中，由于域生长动力学的抑制，明显的不通约（IC）状态，其中热力学等效四种类型的AF域，A，B，C，D，准规则地沿b轴（如A/D/C/B/A/D...）具有相移π/2，用 x=0.00 替代样品中看到的 AF 状态作为低温状态，保持磁相边界的形状。