Click here to view fulltext PDF

Permanent link:
https://www.ias.ac.in/article/fulltext/boms/029/06/0633-0636

Manganites; magnetoresistance; low temperature resistivity; spin polarized tunneling.

The low temperature resistivity and magnetoresistance of bulk samples of La_1–𝑥K_𝑥MnO₃ has been investigated between 10 K and 300 K with and without the magnetic field (𝐻 = 0.8 T). All the samples show metal–insulator transitions with Curie temperature (𝑇_C) ranging between 260 K and 309 K. At temperature below 60 K, the K-doped manganites exhibit a shallow minimum, which disappears under an applied field of 0.8 T. This field dependent minimum in resistivity, observed in K-doped lanthanum manganites is explained in the light of intergrain tunneling of the charge carriers between anti-ferromagnetically coupled grains of the polycrystalline samples. The field variation of magnetoresistance below 𝑇_C follows a phenomenological model which considers spin polarized tunneling at the grain boundaries. The intergranular contribution to the magnetoresistance is separated out from that due to spin polarized tunneling part at the grain boundaries. The temperature dependence of intrinsic contribution to the magnetoresistance follows the prediction of the double exchange model for all values of field at 𝑇 < 𝑇_C.

Soma Das¹ T K Dey¹

1. Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur 721 302, India

Published

November 2006