Spin glass behavior in nanogranular La0.25Ca0.75MnO3 manganites

The magnetic properties of two nanogranular La0.25Ca0.75MnO3 manganites with different average grain sizes have been studied. Besides the well-known exchange bias effect and the appearance of ferromagnetic clusters in the grains of both samples, the results show the occurrence of an antiferromagnetic transition and spin-glass properties. Both samples are described as core–shell magnetic systems, whose main difference is found in the interface between the outer ferromagnetic and the inner antiferromagnetic phases of the grains. • Nanogranular manganites show antiferromagnetism in magnetic measurements.• Exchange bias effect was observed in magnetic hysteresis cycles.• Spin-glass properties were detected at low temperatures.• A core-shell model was applied to describe the results in both samples.• These features have nothing to do with usual properties of nanoparticle manganites.