Analysis of power loss in La0.7Sr0.3MnO3 perovskite

The power loss P-L in La0.7Sr0.3MnO3 polycrystalline samples has been measured with different frequencies (f) and amplitudes of flux density (Bp), and the effect of temperature on P-L was also studied. It is found that when f is below 10 kHz, P-L is proportional to B-p(2.68) or B-p(1.58) as B-p is lower or higher than an inflexion around 1090 G s, respectively, indicating that hysteresis loss plays a major role. For high frequencies, P-L approaches an empirical expression of B(p)(2.20-2.08)f(1.59-1.49) when B-p is more than 500 G s. This case can be mainly explained by classical skin effect. However, for B-p around 100 G s, P-L, respectively, obeys the f(1.75) and f(1.12) law as f is lower and higher than 500 kHz, which is just larger than the relaxation frequency (similar to 205 kHz) of domain walls. This result indicates that the total power loss is mainly dominated by skin effect together with microeddy-current loss that is associated with domain wall motions in the same measuring frequency range. In addition, with increasing temperature up to 348 K, an obvious discrepancy in the plots of P-L versus f or B-p occurs due to wane of domain walls. (c) 2005 Elsevier B.V. All rights reserved.