Origin of the martensitic and austenitic phase transition in core-surface smart nanoparticles with size effects and hysteretic splitting

Yalçın O., ERDEM R., Özüm S.

JOURNAL OF APPLIED PHYSICS, vol.115, no.5, 2014 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 115 Issue: 5
  • Publication Date: 2014
  • Doi Number: 10.1063/1.4864489
  • Journal Name: JOURNAL OF APPLIED PHYSICS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Akdeniz University Affiliated: Yes

Abstract

Blume-Emery-Griffiths model is used to study the effects of the bilinear and biquadratic exchange interactions as well as crystal field interaction on the magnetic properties of core-surface smart nanoparticles. From the minimization of the free energy in pair approximation in Kikuchi version, a set of equations for the bond variables and magnetization are derived. Based on the numerical solutions of these equations, magnetization and hysteresis curves are obtained. Besides the first-and second-order phase transitions, martensitic and austenitic phase regions are observed in the phase diagrams of homogeneous and composite nanoparticles and the origin of martensitic transitions (MT)-austenitic transitions (AT) is investigated. It is found that MT-AT occurred for a nonzero biquadratic exchange parameter. On the other hand, nonzero single-ion anisotropy caused the hysteretic splitting in core-surface type nanoparticles. Martensitic and austenitic results of nanoparticles agree with the experimental results in literature. (c) 2014 AIP Publishing LLC.