Effect of strain on the magnetic and transport properties of the composite manganites, La₂/₃Ca₁/₃MnO₃/yttria-stabilized zirconia

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The magnetic and transport properties have been investigated for the composite polycrystalline manganites, (1-x)La₂/₃Ca₁/₃MnO₃/(x)yttria-stabilized zirconia ((1-x)LCMO/(x)YSZ), at various YSZ fractions, x, ranging from 0 % to 15 %. The ac magnetic susceptibility, χ(T), DC magnetization, M(T), temperature dependent resistivity, ρ(T) and thermoelectric power (TEP), S(T), have been measured. It was found, surprisingly, that a TEP peak showed up in the magnetic transition region for the sample with the x even as little as 0.75 %. The magnetic transition temperature reaches the minimum value as x increases from 0 % to 4.5 % and goes up as x increases further. Several possible factors such as the effect of strain, the finite size effect, and the effect of magnetic tunnelling coupling, etc., in affecting the above physical properties of the composite manganites have been studied carefully. The strain induced by the YSZ/LCMO boundary layer (BL) was identified as the leading factor to account for the x dependence of these properties. It demonstrates that the effect of strain could be important in the bulk manganites as in the film sample.