EFFECT OF SPIN FLUCTUATIONS ON THE MAGNETIC EQUATION OF STATE OF FERROMAGNETIC OR NEARLY FERROMAGNETIC METALS
EFFECT OF SPIN FLUCTUATIONS ON THE MAGNETIC EQUATION OF STATE OF FERROMAGNETIC OR NEARLY FERROMAGNETIC METALS
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DOI：
10.1088/0022-3719/18/22/017
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发表时间：
1985-01-01
期刊：
影响因子：
--
通讯作者：
TAILLEFER, L
中科院分区：
文献类型：
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作者：
LONZARICH, GG;TAILLEFER, L
作者提出了一个定量模型的磁性状态方程的近或弱铁磁金属在低温下，其中包括传统的斯通纳理论所产生的局部磁化强度的波动增强的校正。该模型考虑到纵向和横向波动的四个物理透明的参数，可以独立地确定从状态方程在T= 0的限制和非弹性中子散射，或直接计算从半经验带结构模型附近的费米能级拟合，例如实验费米表面积。对于那些最近确定的弱自旋极化金属Ni 3 Al的相同数量级的参数，该模型产生约二次的温度依赖性的自发磁化强度在很宽的范围远低于居里温度（TC），近线性的逆磁化率远高于TC，和近线性的磁等温线（Arrott图）在高磁场。这些结果与在许多磁性金属中观察到的在低温下接近铁磁不稳定性的行为定性一致。对于Ni 3 Al的模型产生良好的定量协议与实验的居里温度Tc的大小，为高低温有效磁矩的比率p eff/p 0，和磁化强度的二次（T2）变化与温度远低于Tc的系数，而不使用任何自由可调参数。最后，作者表明，该模型还提供了一个很好的定量描述的顺磁磁化率和转变温度的更复杂的磁性系统MnSi，唯一的其他不饱和磁性金属的所有微观参数是众所周知的。
The authors present a quantitative model for the magnetic equation of state of nearly or weakly ferromagnetic metals at low temperatures which includes corrections to conventional Stoner theory arising from enhanced fluctuations in the local magnetisation. The model takes account of both longitudinal and transverse fluctuations in terms of four physically transparent parameters which may be determined independently from the equation of state in the T= 0 limit and from inelastic neutron scattering, or calculated directly from a semi-empirical band structure model near the Fermi level fitted for example to experimental Fermi surface areas. For parameters of the same order of magnitude as those recently determined in the weakly spin-polarised metal Ni 3 Al, the model yields approximately a quadratic temperature dependence of the spontaneous magnetisation over a wide range well below the Curie temperature (T c), a nearly linear inverse susceptibility well above T c, and nearly linear magnetic isotherms (Arrott plots) at high magnetic fields. These results are qualitatively consistent with the behaviour observed in many magnetic metals near the ferromagnetic instability at low temperatures. For Ni 3 Al the model yields good quantitative agreement with experiment for the magnitude of the Curie temperature T c, for the ratio p eff/p 0 of the high-to low-temperature effective magnetic moments, and for the coefficient of the quadratic (T 2) variation of the magnetisation with temperature well below T c, without the use of any free adjustable parameters. Finally the authors show that the model also provides a good quantitative description of the paramagnetic susceptibility and transition temperature of the more complex magnetic system MnSi, the only other unsaturated magnetic metal for which all of the microscopic parameters are well known.