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Abstract |
High Temperature Magneto-Acoustic
Anomalies in Active Material for Parametric Phase Conjugation
R.V.Klopotov, L.M.Krutyansky,
V.L.Preobrazhensky (Wave Research Center of the General Physics Institute RAS)
e-mail:
roman_k@orc.ru
The
results of measurements of the temperature dependence of sound velocities in
magnetostrictive ceramics based on Ni Fe2O4 composition are presented. This
kind of magnetic material is used as an active element of the supercritical
ultrasonic wave phase conjugator [1]. The measurements were made for
longitudinal and shear waves by the resonance method in the interval 300- 740 K
at several values of external magnetic field strength. Anomalous temperature
dependence of the resonance frequencies, increase of magneto-elastic coupling
coefficient and enhancement of acoustic nonlinearity were observed near 630 K.
Bistability of the resonance excitations and auto-modulation phenomena are
detected in this temperature region. Observed magneto-acoustic behavior is typical
for magnetic materials in the vicinity of spin reorientation instability [2].
Possibilities to use high temperature anomaly for improvement of efficiency of
supercritical phase conjugation in magnetic ceramics are discussed. References:
1. A.P.Brysev, L.M.Krutyansky,
V.L.Preobrazhensky. Uspekhi Phys. Nauk, v.168, p.877 (1998). 2.
V.I.Ozhogin, V.L.Preobrazhensky.
Journ. Magn. & Magn. Materials, v.100, p.544 (1991).
Section
: 10