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Title: Calculating the spontaneous magnetization and defining the Curie temperature using a positive-feedback model

A positive-feedback mean-field modification of the classical Brillouin magnetization theory provides an explanation of the apparent persistence of the spontaneous magnetization beyond the conventional Curie temperature—the little understood “tail” phenomenon that occurs in many ferromagnetic materials. The classical theory is unable to resolve this apparent anomaly. The modified theory incorporates the temperature-dependent quantum-scale hysteretic and mesoscopic domain-scale anhysteretic magnetization processes and includes the effects of demagnetizing and exchange fields. It is found that the thermal behavior of the reversible and irreversible segments of the hysteresis loops, as predicted by the theory, is a key to the presence or absence of the “tails.” The theory, which permits arbitrary values of the quantum spin number J, generally provides a quantitative agreement with the thermal variations of both the spontaneous magnetization and the shape of the hysteresis loop.
Authors:
 [1]
  1. Department of Electronics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada)
Publication Date:
OSTI Identifier:
22275780
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 3; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CURIE POINT; DOMAIN STRUCTURE; FEEDBACK; FERROMAGNETIC MATERIALS; FERROMAGNETISM; HYSTERESIS; MAGNETIZATION; MEAN-FIELD THEORY; SPIN; TEMPERATURE DEPENDENCE