Low Temperature Physics: 28, 556 (2002); https://doi.org/10.1063/1.1496667 (6 pages)
Физика Низких Температур: Том 28, Выпуск 7 (Июль 2002), c. 774-780    ( к оглавлению , назад )

Exchange interaction and magnetoresistance in La2/3Ca1/3MnO3 : experiment and models

A. B. Beznosov, B. I. Belevtsev, E. L. Fertman, and V. A. Desnenko

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: beznosov@ilt.kharkov.ua

D. G. Naugle, K. D. D. Rathnayaka, and A. Parasiris

Department of Physics, Texas A & M University, College Station, TX 77843, USA

Received March 5, 2002


The magnetization M(T) and electrical resistivity r(T) of a La2/3Ca1/3MnO3 film have been studied in the temperature range 5 K £ T £ 320 K in the magnetic field intervals 10 Oe £ H £ 400 Oe and 0 £ H £ 50 kOe, respectively. It is found that the M(T)/M(0) value is larger than that predicted by the conventional molecular field model below the Curie point T = 267 K, and that the ln r(T) dependence is close to linear in the temperature range 80 K < T < 200 K (accordingly, ln r/T is constant in this region). A model of the electrical conductivity and magnetoresistivity of the system describing qualitatively the experimental results is proposed (the Dmt model). The model includes a thermally activated (with characteristic energy D) mechanism of conductivity, dependence of the concentration and the effective mass (m) of the itinerant charge carriers on the magnetization, as well as scattering (with characteristic time t) of the charge carriers by static breakings of the translational symmetry, thermal fluctuations of the magnetic order, and phonons.

75.30.Vn -
72.80.Ga - Transition-metal compounds
81.05.-t - Specific materials: fabrication, treatment, testing, and analysis