采用溶胶-凝胶法制备La0．25 Ca0．75 MnO3纳米颗粒，并分别在空气和氩气气氛下退火，获得颗粒尺寸约为100 nm的两种样品.对两种样品磁滞回线的测量研究表明：与空气气氛下退火相比，氩气气氛退火后样品中的氧原子配比减少，减弱了颗粒表面未补偿自旋的铁磁耦合，从而减弱了交换偏置效应.%Polycrystalline nanoparticles of La0. 25 Ca0. 75 MnO3 were prepared by sol-gel method, and annealed in air and Ar respectively. The average size of nanoparticles was about 100 nm. The magnetic hysteresis loops for the samples were measured. The results indicate that the oxygen content decreases as nanoparticles are annealed in Ar atmosphere, and the exchange bias effect reduces due to the weakened ferromagnetic coupling between the uncompensated surface spins.
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