Effect of suppression of local distortion on magnetic, electrical and thermal transport properties of Cr substituted bi-layer manganite LaSr${}_2$Mn${}_2$O${}_7$

Abstract

We have investigated magnetic, electrical and thermal transport properties (Seebeck effect and thermal conductivity) of LaSr${}_2$Mn${}_{2-y}$Cr${}_y$O${}_7$ polycrystalline samples ($y$=0.1, 0.2, 0.4 and 0.6). The Cr${}^{3+}$ substitution for Mn${}^{3+}$ sites causes a removal of $d_{x^2-y^2}$ orbital of $e_g$-electron resulting in a volume shrinkage of lattice. Magnetic measurements reveal the appearance of a glassy behavior for Cr-doped samples, accompanied by both a collapse of the A-type antiferromagnetic structure and the growth of ferromagnetic clusters. Cr-doping effect on electrical transport strongly enhances an insulating behavior over a wide range of temperature, while it suppresses a local minimum of thermoelectric power at lower temperatures. The phonon thermal conduction gradually rises with increasing Cr content, which is contradictory to a typical impurity effect on thermal conductivity. We attribute this to a suppression of local lattice distortion through the introduction of Jahn-Teller inactive ions of Cr${}^{3+}$.

8 pages, 9figures

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Cited by in corpus (1)

• Magnetotransport properties of La${}_{1-x}$Ca${}_x$MnO${}_3$ (0.52 $\le x\le$ 0.75): signature of phase coexistence