Monte Carlo and mean field calculations of the magnetocaloric effect of ferromagnetically interacting clusters

Conference · Tue Jan 01 00:00:00 EST 1991

OSTI ID:5616380

Bennett, L H; McMichael, R D; Swartzendruber, L J; Shull, R D ^[1]; Watson, R E ^[2]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (USA)
2. Brookhaven National Lab., Upton, NY (USA)

The magnetic entropy change of a ferromagnet induced by an application of a magnetic field is greatest in the temperature region near the Curie point, and the magnitude of the effect is expected to rise monotonically with the size of individual moments which make up the material. We explore the case of nanocomposite materials with ferromagnetically interacting clusters having large cluster magnetic moments as a function of cluster size. As cluster size increases, both Monte Carlo and mean field calculations show a decrease in the entropy change at {Tc} for a given applied field and constant total magnetic moment, and an increase in the entropy change well over {Tc}. In addition, for the first time, we present a comparison of the results of mean field and Monte Carlo calculations of the magnetocaloric effect in classical Heisenberg ferromagnets. Previous calculations of the magnetocaloric effect have taken the mean field approach, which is known to underestimate the spontaneous magnetization below {Tc}. These issues are relevant to devices employing magnetic refrigeration. 11 refs., 2 figs.

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5616380
• Report Number(s): BNL-46292; CONF-910903-3; ON: DE91014792
• Resource Relation: Conference: International conference on magnetism, Edinburgh (United Kingdom), 1-7 Sep 1991
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
ENTROPY
FERROMAGNETIC MATERIALS
MAGNETO-THERMAL EFFECTS
ADIABATIC DEMAGNETIZATION
COOLING
CURIE POINT
MAGNETIC FIELDS
MAGNETIC MOMENTS
MAGNETIC REFRIGERATORS
MEAN-FIELD THEORY
MEETINGS
MONTE CARLO METHOD
SOLID CLUSTERS
SUPERPARAMAGNETISM
DEMAGNETIZATION
MAGNETIC MATERIALS
MAGNETISM
MATERIALS
PHYSICAL PROPERTIES
REFRIGERATORS
TEMPERATURE EFFECTS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
360603* - Materials- Properties