Zeroth-Order Nucleation Transition under Nanoscale Phase Separation

TL;DR

This paper investigates a nanoscale phase-separated system with ferromagnetic and paramagnetic phases, revealing a zeroth-order nucleation transition characterized by a sudden appearance of paramagnetic phase at finite concentration.

Contribution

It introduces a renormalized Hamiltonian for heterophase mixtures and uncovers a novel zeroth-order nucleation transition at finite temperature.

Findings

Identification of a zeroth-order nucleation transition.

Finite paramagnetic phase appears via a jump at the transition.

System stability depends on temperature and interaction parameters.

Abstract

Materials with nanoscale phase separation are considered. A system representing a heterophase mixture of ferromagnetic and paramagnetic phases is studied. After averaging over phase configurations, a renormalized Hamiltonian is derived describing the coexisting phases. The system is characterized by direct and exchange interactions and an external magnetic field. The properties of the system are studied numerically. The stability conditions define the stable state of the system. At a temperature of zero, the system is in a pure ferromagnetic state. However, at finite temperature, for some interaction parameters, the system can exhibit a zeroth-order nucleation transition between the pure ferromagnetic phase and the mixed state with coexisting ferromagnetic and paramagnetic phases. At the nucleation transition, the finite concentration of the paramagnetic phase appears via a jump.