RESEARCH ON NEW GIANT MAGNETOSTRICTIVE RARE EARTH-TRANSITION METAL INTERMETALLIC COMPOUNDS, AND CONTROL OF HIGH MAGNETOMECHANICAL COUPLING

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Research work on new giant magnetostrictive materials from a physical view point and a development work to attain high magnetomechanical coupling were carried out.[1] Research on new giant magnetostrictive compounds(1-1) RCo_3 compoundMagnetostriction of RCo_3 at room temperature is -25x10^<-6>, -155x10^<-6>, -65x10^<-6>, 760x10^<-6>, 80x10^<-6> for R=Y, Pr, Sm, Gd, Tb and Dy, respectively. The magnetostriction of TbCo_3 reaches 2680x10^<-6> at 77K, which is comparable to the typical giant magnetostrictive compound TbFe_2.(1-2) Tb(Fe_<1-x>M_x)_2 compoundA substitution of M elements (M=Co, Ni, Mn, Cr, Ti, V) to the Fe site in TbFe_2 causes a reduction of magnetostriction. However it improves a magnetic softness in the case of M=Ti, Cr, Mn and Co.[2] Development of the giant magnetostrictive materials with a high magnetomechanical coupling by forming nanocrystallite and amorphous phase(2-1) Rapidly quenching of TbFe_2 compoundAs a quenching velocity increases from 8m/s to 32m/s, the crys … More talline size decreases from 400A to 250A and the coercive force drops to 9000e. This indicates that a magnetocrystalline anisotropy can be suppressed by a formation of nanocrystalline of giant magnetostrictive compounds similarly to soft magnetic materials. On the other hand, a high magnetoelastic coupling was not attained by an amorphization of Fe_2Tb.(2-2) Rapidly quenching of SmFe_2 compoundMgCu_2 phase is formed in the Sm_<1-x>Fe_x system around x=0.66. The magnetostriction is less than -500x10^<-6> for Sm_<0.34>Fe_<0.66>, but reaches -1100x10^<-6> for Sm_<0.35>(Fe_<0.5>Co_<0.5>)_<0.65>. The magnetic softness was not obtained in a rapidly quenched SmFe system.(2-3) Measurement apparatus for dynamic magnetomechanical couplingThe apparatus is composed of bias magnetic field, ac exciting field, impedance analyzer and personal computer for system control and data analysis. A dynamic magnetomechanical coupling for thin ribbons having L/D more than 15 can be measured in the accuracy within 5%. Less