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Dilution of 2D antiferromagnetism by Mn site substitution in La{_1}Sr{_2}Mn{_{2-x}}Al{_x}O{_7}

Sunil Nair·A. Banerjee
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Abstract

We report the effect of Al substitution on the Mn site of the bilayered half doped manganite La{_1}Sr{_2}Mn{_2}O{_7}. This substitution dilutes the magnetically active Mn-O-Mn network without introducing an appreciable distortion in the lattice and ionic considerations leads to a predominant reduction of Mn{^{4+}} with increasing Al. The rate of fall of the long range antiferromagnetic transition temperature as a function of substitution is seen to match well with established quasi 2D Heisenberg systems indicating that the nature of magnetic interactions in this quasi 2-D system is of the short range Heisenberg type. The magnetic contribution of the specific heat estimated using Fisher's relation could be fitted with a function incorporating the presence of a gapped Fermi surface appropriate for this type of systems. The resistivity was seen to increase as a function of substitution due to the weakening of the double exchange within the ferromagnetic layers of these A type of antiferromagnets and justifiably, in the paramagnetic region the data could be fitted to Mott's equation for the variable range hopping of polarons in 2 dimensions.

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Sunil Nair, A. Banerjee. 2003-12-08. Dilution of 2D antiferromagnetism by Mn site substitution in La{_1}Sr{_2}Mn{_{2-x}}Al{_x}O{_7}. https://doi.org/10.1103/physrevb.70.104428

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