Critical exponents of the La0.7Sr0.3MnO3, La0.7Ca0.3MnO3, and Pr0.7Ca0.3MnO3 systems showing correlation between transport and magnetic properties

Journal of Applied Physics - Tập 98 Số 10 - 2005
Subhrangsu Taran1, B. K. Chaudhuri1, Sandip Chatterjee2, Hangfu Yang3, S. Neeleshwar4, Y. Y. Chen4
1Indian Association for the Cultivation of Science Solid State Physics Department, , Jadavpur, Kolkata-700032, India
2Government College of Engineering and Textile Technology Department of Physics, , Serampore-712201, West Bengal, India
3National Sun Yat Sen University Department of Physics, , Kaohsiung, Taiwan, Republic of China
4Institute of Physics, Academia Sinica, Taipei, Taiwan Republic of China

Tóm tắt

From the low-temperature (down to 10K) dc-magnetization data of the La0.7Sr0.3MnO3 (LSM), La0.7Ca0.3MnO3 (LCM), and Pr0.7Ca0.3MnO3 (PCM) systems, we estimated the critical exponents β, γ, and hence δ from the analysis of the modified Arrot plots. The exponent β estimated for the LCM system is less than that predicted by Heisenberg model and resides within the zone predicted by Ising model while for the LSM sample, β is higher than that predicted from the Heisenberg model which is considered to be due to the presence of dipole-dipole interaction arising from the large spin moment in the LSM system. The magnetization data of the PCM system cannot be fitted to the modified Arrot plots, which suggest highly inhomogeneous ground state even under 5T magnetic field. Both LSM and LCM have almost equal values of γ. Seebeck coefficient data indicate a crossover from higher-temperature n-type to lower-temperature p-type conductivity behavior in both LSM and LCM systems, while the semiconducting PCM system shows p-type conductivity throughout the temperature range (300–80K). It is noticed that for LSM system TC (Curie temperature) and TMI (metal-insulator transition temperature) are almost equal (∼360K), whereas for the LCM system there exist a large difference between TC and TMI (TC∼245K and TMI∼265K), which may give some idea regarding the critical behavior of the respective samples.

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Journal of Applied Physics

Tập 98 Số 10

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