Temperature effect on dipolar and exchange interactions for SmCo5 + Fe65Co35 nanocomposite powders

• Published in: Journal of applied physics 2012-04, Vol.111 (7)
• Main Authors: Muñoz Ortega, L. P., Elizalde Galindo, J. T., Farias Mancilla, J. R., Santillan, C. R., Matutes Aquino, J. A.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3672070

DC magnetization measurements were used to determine the temperature dependencies of the magnetic properties for (90%wt)SmCo5 + (10%wt)Fe65Co35 nanocomposite powders synthesized by mechanical milling and subsequent annealing. The annealing conditions were T equal to 1073 K and time, t, equal to 1.5, 3.0, 4.5, 6.0 min. Maximum magnetization decreased upon cooling in temperature range from 290 to 10 K. Coercivity increased its value to a maximum at the lowest temperature. On the other hand, hysteresis loops collected at low temperatures showed a “knee” in the second quadrant of the demagnetization curve, which suggests that dipolar interactions are becoming stronger than intergrain exchange coupling as temperature is lowered. This low temperature reduction of exchange interactions is confirmed by the temperature dependence of the exchange coupled volume ratio, R. Finally, the temperature effect on magnetic properties is explained on the basis of anisotropy enhancement and reduction of thermal fluctuations as temperature decreases.