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Phase Transitions in Ordered and Disordered Ferrimagnets. II. Experimental Results
Author(s) -
Haug M.,
Fähnle M.,
Kronmüller H.,
Haberey F.
Publication year - 1987
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221440136
Subject(s) - ferrimagnetism , condensed matter physics , homogeneous , critical exponent , ferromagnetism , exponent , materials science , phase transition , phase (matter) , physics , magnetization , magnetic field , thermodynamics , quantum mechanics , linguistics , philosophy
The magnetic phase transition is investigated by a vibration magnetometer for the homogeneous ferrimagnet Fe 3 O 4 and the structurally disordered ferrites Zn x Ni 1− x Fe 2 O 4 with x = 0, 0.25, 0.5, and 0.75. For both ordered and disordered ferrimagnets the asymptotic critical exponents are compatible with the ones of a homogeneous 3d‐Heisenberg ferromagnet. Outside the asymptotic critical regime there is a strong effect of the structural inhomogeneities on the thermodynamic behaviour. In close analogy to the case of disordered ferromagnets, the effective Kouvel‐Fisher exponent γ( T ) first increases with increasing temperature T for disordered systems, as predicted by the correlated molecular field theory and by Monte Carlo computer simulations, whereas it initially decreases for a homogeneous ferrimagnet. Anomalies in the modified Arrott plots at low fields are discussed.