Magnetic Anisotropy of Single-Domain Particles

V. I. Petinov

Institute of Problems of Chemical Physics, Russian Academy of Sciences,
pr. Akademika Semenova 1, Chernogolovka, Moscow oblast, 142432 Russia
e-mail: petinov@icp.ac.ru

Received July 16, 2012; in final form, February 6, 2013

Abstract—The competition between uniaxial and cubic magnetic anisotropies of single-domain particles is
analyzed theoretically. As long as K_1c/K_1u < 5 (K_1c and K_1u are the first constants of the crystallographic and
uniaxial anisotropies), the value of K_1u noticeably affects coercive force H_c and relative residual magnetization
j_r of particle ensembles. If the uniaxial anisotropy direction coincides with crystallographic axis 111 or 100,
the dependences of H_c and j_r on ratio K_1c/K_1u have a minimum. The competition between the induced uniaxial
anisotropy and cubic anisotropy was detected experimentally when the effect of temperature T on the H_c(T) and
j_r(T) dependences for single-domain spherical particles of magnetic 3d alloys and -Fe₂O₃ oxide was investi-
gated. For all single-domain particles studied here, the effect of crystallographic anisotropy on H_c and j_r is man-
ifested at low temperatures, while uniaxial anisotropy plays a decisive role in the temperature range T > 250 K.
The effect of second constant K₂ on H_c and j_r of ensembles of single-domain particles with uniaxial and cubic
anisotropies is investigated theoretically. It is shown that the value of K₂ may substantially change the value of
H_c for a particle ensemble, preserving the value of j_r unchanged.

DOI: 10.1134/S1063784214010137

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