Unusually large deformation coefficients were observed by applied electric fields in conducting Mn-Zn ferrite crystals. The observed electrostrictive coefficients (
X) defined by
S=1/2
XE2 (
S: strain,
E: electric field) were of the order of magnitude of 10
-10(m/V)
2, which were 10
11 times larger than the electrostrictive coefficient of BaTiO
3. The observed strains are due to a magnetostrictive effect from the magnetic field induced by the electric current through the crystal. The electric signals due to elastic strains were obtained by using a dc biasing current.
A large piezoelectric effect was also observed in the same Mn-Zn ferrite crystals under magnetic fields both parallel to and perpendicular to the electric field. The induced strains were correctly given by the relation:
S=
d•
E, The piezoelectric d-constants were dependent upon the magnetic field and crystallographic orientations and were of the order of magnitude of 10
-10 C/N under a suitable magnetic field. These are, respectively, about 100 times larger than and of the same order of magnitude as the piezoelectric constant of a quartz crystal and a PZT ceramic element.
The emf voltages due to elastic strains were obtained as a result of the inverse processes mentiond above.
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