E. Z. Valiev and V. I. Bobrovskii

ON THE ABNORMAL BEHAVIOR OF COMPRESSIBILITY IN THE Fe₇₂Pt₂₈ INVAR ALLOY

In the paper, we apply our previously developed phenomenological theory of magnetoelastic interaction to a systematic description of the behavior of the elastic and magnetic characteristics of invars under pressure. This approach allows us to explain a seemingly paradoxical decrease in the compression moduli of the Fe₇₂Pt₂₈ invar under pressure alongside the simultaneously observed standard increase in the shear moduli. This paradox of compressibility in invar alloys proves to be due to two factors, namely the existence of a minimum of the compression modulus near the Curie point and the pressure-induced shift of the Curie point. Note that, in addition to a qualitative explanation of the unusual behavior of compressibility in invars, our formulas provide a good quantitative agreement with experiment. Our conclusions are supported by numerical calculations performed with the use of formulas based on the Heisenberg model with allowance made for magnetoelastic interaction.

Acknowledgment: The research was carried out at the IMP Neutron Material Science Complex under the state assignment of the Ministry of Science and Higher Education of the Russian Federation for the IMP UB RAS.

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