soft-magnetic materials that exhibit appreciable magnetostriction.
Magnetostrictive materials are used as converters of electromagnetic energy (for example, into mechanical energy), and for pressure transducers. Magnetostrictive materials include nickel and alloys such as Fe-Al (Alfer), Fe-Ni (Permalloy), Co-Ni, Fe-Co, and Co-Fe-V (Permendur); several ferrites (CoFe2O4 and NiFe2O4); and some rare earths and their alloys and compounds. Nickel has good magnetostrictive, mechanical, and anticorrosion properties. Permendur has large values of saturation magnetostriction Δs and magnetization. The ferrites have high specific electric resistivity and corrosion resistance; they are also the least expensive magnetostrictive materials.
Table 1 shows the initial and reversible magnetic permeability μa and μr, respectively, of magnetostrictive materials; the magnetostriction constant α = ((∂σ/∂β)ε>), which characterizes the dependence of mechanical strain on the magnetic induction B of the specimen under conditions of constant deformation €; the sensitivity β = (∂β/∂σ)h of magnetostrictive materials with respect to strain in a constant magnetic field H\ and the coefficient of gyromagnetic coupling k, which is essential for magnetostrictive ultrasonic emitters (the ratio of the mechanical energy, which was converted by the emitter, to the electromagnetic energy supplied).
|Table 1. Main characteristics of most important magnetostrictive materials|
(% by mass)
|μa||μr||k||λs × 106|
|Note: 1 dyne/(gauss-cm2) = 103 N/(T-m2); 1 (gauss-cm2)/dyne = 10-3 (T.m2)/ N|
|Co-Ni||18 Co, 82 Ni||1,000||200||19||127||0.35||-25|
|Permendur||49 Co 2 V; remainder Fe||600||80||11||83||0.30||65|
|Iu14 (Alfer)||14 Al, 86 Fe||1,000||250||8||65||0.24||50|
REFERENCESTurichin, A. M. Elektricheskie izmereniia neelektricheskikh velichin, 4th ed. Moscow-Leningrad, 1966.
Gershgal, D. A., and V. M. Fridman. Urtrazvukovaia apparatura. Moscow-Leningrad, 1961.
Redkozeme’nye ferromagnetiki i antiferromagnetiki Moscow, 1965.
Table 1. Main characteristics of most important magnetostrictive materials