On the induction of the first-order phase magnetic transitions by acoustic vibrations in MnSi
S. A. Pikin
Shubnikov Institute of Crystallography of Federal Scientific Research Centre
"Crystallography and Photonics" of Russian Academy of Sciences, 119333 Moscow, Russia
Abstract
The main result of the paper contains the conclusion that the magnetic
phase transition in MnSi always remains first order at any temperature and
magnetic field. In these aims, a model of coupling of an order parameter with
other degrees of freedom is used. The coupling of magnetic order parameters with
long-wave acoustic phonons, in the presence of the nonsingular parts of the bulk
and shear moduli, a first-order transition occurs, participle near the
transition the heat capacity and the compressibility remain finite, if in the
system without allowance of the acoustic phonons the heat capacity becomes
infinite. The role of the Frenkel heterophase fluctuations is discussed. The
impurity effect shows that, for some phases, the heat capacity of the system
remains continuous and finite at the transition point. It is supposed that the
transition is progressively smoothed by these fluctuations at the application of
the magnetic field.