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Precritical anomalous scaling and magnetization temperature dependence in cubic ferromagnetic crystals
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DOI：10.1103/PhysRevB.111.104433.png)
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Abstract
En 中文
Recent developments in spintronics have drawn renewed attention to the spin dynamics of cubic ferromagnetic crystals EuO and EuS. These ferromagnets have the simplest possible magnetic structure, making them the most suitable systems for testing various theoretical models of magnetic materials. A commonly used Weiss meanfield approximation (MFA) provides only a qualitative description of the magnetization temperature dependence M(T ). We develop a consistent theory for M(T ) based on the perturbation diagrammatic technique for spin operators. Our theory is in excellent quantitative agreement with the experimental dependence of M(T ) for EuO and EuS throughout the entire temperature range from T = 0 to Curie temperature TC. In particular, our theoretical dependence M(T ) demonstrates a scaling behavior M(T ) proportional to (TC - T )beta & lowast; with the scaling index beta & lowast; approximate to 1/3 in a wide range of temperatures, in agreement with the experimentally observed apparent scaling in EuO and EuS. The scaling behavior with beta & lowast; approximate to 1/3 is manifested in the temperature range T <= TC where corrections to the magnetization due to its fluctuations 8M(T ) <= M(T ). To distinguish it from the narrow critical range T approximate to TC with 8M(T ) > M(T ), we term this T-range precritical. The precritical corrections 8M(T ) are still large enough to affect the M(T ) behavior. The index beta & lowast; fundamentally differs from the normal scaling index beta MFA = 1/2 predicted by the MFA, which neglects the magnetization fluctuations. We refer to the apparent magnetization scaling with beta & lowast; approximate to 1/3, which emerges in our theory, as precritical anomalous.
Keywords:
NEUTRON-SCATTERING
EUO
DYNAMICS
EQUILIBRIUM
EXCHANGE
MODEL
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3.7
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15.4W
Citations:
41.0W
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