https://doi.org/10.1007/s100510050756
Quantum theory of the magneto-optical effect induced by Ni2+ ions in barium ferrites
1
Department of Physics, Nanjing University, Nanjing 210008, and Department of
Physics, Teacher's College,
Yangzhou University, Yangzhou 225002, P.R. China
2
CCAST (World Laboratory), PO Box 8730, Beijing 100080, and Department of Physics,
Nanjing University, Nanjing 210008, and National Key Laboratory of Magnetism, Institute
of Physics, Chinese Academy of Sciences, Beijing 100080,
P.R. China
3
Laboratoire des Champs Magnétiques Intenses, CNRS/MPI, B.P. 166, 38042 Grenoble Cedex 9,
France
Received:
7
January
1998
Published online: 15 May 1999
To reveal the physical origin of the giant magneto-optical enhancement of Ni2+
ions in barium ferrite, quantitative calculations of the contributions of both the
intra-ionic electric dipole transition between the and
configurations of the Ni2+ ions and the intra-ionic electric dipole
transition induced by odd-parity crystal field terms are presented. It is deduced
that the
transition is important in the origin of the
considered magneto-optical enhancement. The most important factor is the Ni-Fe
superexchange interaction; since it is strong enough, the Faraday rotation produced by
the Ni2+ ions is large though the energy difference between the
and
configurations is large. It is demonstrated that though the intra-ionic electric
dipole
transition does produce Faraday rotation peaks in the visible range, their
magnitude is too small to explain the observed Faraday rotation. The effect of the
spin-orbit interaction on the Faraday rotation is analysed. The spin-orbit interaction
of the ground configuration plays a very important role in the occurrence of Faraday
effects, but the Faraday rotation does not increase linearly with the strength of the
spin-orbit coupling. On the contrary, the spin-orbit interaction of the excited
configuration has almost no effect on the Faraday rotation. It is shown that the mixing
of the different multiplets of the ground term induced by the crystal field has a
great influence on the magneto-optical properties.
PACS: 78.20.Ls – Magnetooptical effects / 75.50.Gg – Ferrimagnetics
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999