Theoretical forecast of the spin reorientational phase transition

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ROLE OF INVESTIGATION OF THE INTERPARTICLE MAGNETIC
INTERACTION IN THE DETERMINATION OF THE SPRT IN THE BaFe12O19
NANOCRYSTAL SYSTEM
Ol’khovik L., Shurinova E.
V.N.Karazin Kharkov National University, Kharkov, Ukraine
[email protected]
The main magnetization curve for the densely packed system of nanocrystals of the highly
anisotropic hexagonal barium ferrite has been obtained and reconstructed with taking into account the
interparticle magnetic interaction. A larger steepness of the reconstructed experimental curve as
compared to the Stoner -Wohlfarth theoretical dependence indicates to the realization of a
spin-reoriented phase transition of the first kind. This is confirmed by a computer simulation of
magnetization curve of the hexagonal crystal for the case of arbitrary orientation of the external
magnetic field and taking into account the surface anisotropy.
It was established that magnetization curves of nanocrystals oriented in the polar angle range
of 90-65O exhibited an anomaly in the form of a jump
An analysis of changes of characteristic surface of anisotropy and its cross section with the
increasing ratio
K2
when going from the macrocrystal to the nanocrystal shows that the surface
K1
anisotropy leads to a change in magnetic structure. As a consequence, apart from the easiest (along
the с axis) direction there appears an additional easy magnetization axis on the basal plane. The hard
magnetization axis comes out of the basal plane and makes an angle to the с axis depending on the
K2
ratio.
K1
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