Magnetic interactions in La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr) manganites

• Magnetic structure of the compounds has been clarified by NPD.
• Magnetic properties of the compounds has been explained using superexchange scenario.
• Mn–O–Fe and Fe–O–Fe superexchange interactions are strongly antiferromagnetic.

Magnetic properties and crystal structure of La0.7Sr0.3Mn1−xMexO3 (Me=Ga, Fe, Cr; x≤0.3) have been studied by neutron powder diffraction and magnetization measurements. It is shown that substitution of manganese ions by chromium or gallium ions (x=0.3) leads to phase separation into antiferromagnetic and ferromagnetic phases whereas replacement by Fe ions stabilizes spin glass state (x=0.3). Ferromagnetic interactions in Cr-substituted compounds are much more pronounced than in Fe- and Ga-doped ones. Magnetic properties are discussed in the model assuming a dominance of superexchange interactions. It is considered that ferromagnetism in the Cr-substituted compositions is associated with nearly equal contributions from positive and negative components of the superexchange interaction between Mn3+ and Cr3+ ions as well as to mixed valence of chromium ions. The spin glass state observed for the Fe-doped sample (x=0.3) is associated with strong antiferromagnetic superexchange between Fe3+–O–Fe3+ and Fe3+–O–(Mn3+, Mn4+).