Naoko Kasai

Thermal Expansion of Au4V

Linear thermal expansion α of Au 4 V in the ordered and disordered states has been measured from 4.2°K to 100°K. An anomaly, which corresponds to the magnetic ordering, has been found in the ordered state. The magnetic entropy estimated from the magnetic contribution α m is (0.55±0.16) R , which suggests a magnetic moment of approximately 1µ B per V atom. The Curie temperature of the ordered Au 4 V is 52±1°K. The electronic contribution to α, α e , and the lattice contribution α L in units of °K -1 are; α e =(0.95±0.05)×10 -8 T and α L =(9.6±0.2)×10 -11 T 3 ( T ≤20°K) in the disordered state and α e =(3.65±0.05)×10 -8 T and α L =(9.1±0.3)×10 -6 C Debye (θ D =245)/3 R ( T ≥60°K) in the ordered state. The pressure dependence of Curie temperature ∂ T c /∂ P in the ordered Au 4 V is estimated to be +0.2°K/kbar. The Gruneisen constants in both states are estimated.

Mössbauer and X-Ray Study of MnTe2

Experiments on the Mossbauer effect of 125 Te and the X-ray diffraction for antiferromagnetic MnTe 2 were performed. Temperature dependence of the spin direction has been observed for a magnetic ordering of the first kind fcc lattice. The angle between the spin direction of Mn and the principal axis of electric field gradient increases from 23° at 4.2 K to 30° at 60 K and decreases to 0° at 70 K. Discontinuous changes are found in hyperfine field and quadrupole splitting at 60 K. An analysis of X-ray diffraction intensities for (742), (732) and (721) reflections shows that u parameter increases by 0.0015 at 60 K as temperature decreases and that Einstein temperature increases from 95 K to 105 K below 60 K. The crystallographic phase diagram of MnTe–Te system is given.