Exchange-coupling properties of La1-xCaMnO3 ferromagnetic/antiferromagnetic multilayers -: art. no. 094429

Compositionally modulated structures consisting of La1-xCaxMnO3 ferromagnetic (FM) layers (x=0.33, 0.4. 0.48) and La1-yCayMnO3 antiferromagnetic (AF) layers (y=0.52, 0.67, 0.75) were grown on (001)LaAlO3 by pulsed laser deposition. Thermomagnetic and isothermal magnetic, magnetotransport measurements reveal an exchange biasing mechanism below a blocking temperature T(B)approximate to 70 K. Between 5 K and TB, the observed exponential thermal decay of coercive (H-c) and exchange biasing (H-EB) fields follows the drop of magnetization (M-FC) in the field-cooling curves. All the experimental results indicate that thermal fluctuations, different from spin-wave demagnetization. give rise to exponential thermal decay of M-FC and determine the observed behavior of H-c and H-EB at low T. The extrapolated values of H-c and H-EB to zero temperature exhibit a quasilinear dependence on the average interfacial concentration xi=(x+y)/2, both decreasing for fixed y=0.67 while x increases or both increasing for fixed x=0.4 while y increases.