THERMAL EXPANSION AND FORCE MAGNETOSTRICTION IN A TERBIUM SINGLE CRYSTAL

Forced magnetostriction and thermal-expansion measurements on a terbium single crystal are reported. The isotropic component of the basal-plane forced magnetostriction is evaluated for applied fields between 17 500 and 19 500 Oe. A peak value of -18.5×10-8/Oe is found at 246°K. Large, positive, field-dependent forced-magnetostriction values are obtained along the 〈0001 〉 axis for fields applied along the 〈1010〉 axis. The field dependence of the 〈0001 〉-axis forced magnetostriction is in agreement with Belov's thermodynamic description in the vicinity of the Curie temperature. A large negative expansion anomaly of - 104×10 -6/deg is obtained at 224°K. The magnetic component of this strain is identificed with the exchange and ordinary magnetostriction, and not only with an ordinary term as was done by Rhyne and Legvold. The large magnetothermal strain of 900×10-6 occurring at the Curie point, and the persistence of the anomalous behavior high in the paramagnetic region can be ascribed to the exchange magnetostriction. Using 〈0001 〉-axis forced strain measurements, a calculation by Belov's method of thermodynamic coefficients yields a value of -47×10-6 /deg at the Curie point. © 1968 The American Institute of Physics.