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5 papers
Theoretical and Mathematical Physics
Magnetic anisotropy of single-domain particles
V. I. Petinov Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432, Russia
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
$\langle$111
$\rangle$ or
$\langle$100
$\rangle$, 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 3
$d$ alloys and
$\gamma$-Fe
$_2$O
$_3$ oxide was investigated. For all single-domain particles studied here, the effect of crystallographic anisotropy on
$H_c$ and
$j_r$ is manifested at low temperatures, while uniaxial anisotropy plays a decisive role in the temperature range
$T >$ 250 K. The effect of second constant
$K_2$ 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
$K_2$ may substantially change the value of
$H_c$ for a particle ensemble, preserving the value of
$j_r$ unchanged.
Received: 16.07.2012
Accepted: 06.02.2013
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