Comprehensive study of high temperature ferromagnetic semiconductor Cd0.82Mn0.18GeAs2

Akhmedbek Y. Mollaev 1Ibrahimkhan K. Kamilov 1Rasul K. Arslanov 1Temirlan R. Arslanov 1Ullubii Z. Zalibekov 1Vladimir M. Novotorzev 2Sergey F. Marenkin 2Irina V. Fedorchenko 2

1. Institute of Physics of DSC, RAS, Makhachkala 367003, Russian Federation
2. Institute of common and inorganic chemistry of the Russian Academy of Sciences (IONX), Moscow 119334, Russian Federation

Abstract

Baric dependencies P≤7 GPa, magnetic field H≤5kOe and dependencies of specific resistivity ρ, Hall coefficient RH dependencies, dependencies of cross magnetic resistance Δρxx/ρ and dependencies of relative susceptibility χ/χ0 in high temperature ferromagnetic semiconductor Cd0.82Mn18GeAs2 have been studied. There were taken several methods for measuring: baric dependencies were measured at rise and fall of hydrostatic pressure using method [1,2], magnetic susceptibility  using frequency method [3], magnetic field dependence using standard method. Structural reversible phase transitions semiconductor–metal at P =5.2 GPa were found on baric dependence ρ(P) and RH(P). One may outline four regions on curve RH(P): P≤0.6 GPa – region of impurity conductivity, P= 0.6 – 1.9 GPa – region of exhaustion, P=1.9 – 4.5 GPa – region of fall of RH (reasons are still in discuss) and P=4.5 – 6.5 – region of phase transition. In the region of phase transition P > 5 GPa, curve comes out for saturation, where electric conductivity σ = 3000 Ω-1 cm-1, and concentration of charge carriers 5×1020cm-3 testifies that there takes place semiconductor–metal transition. Magnetic phase transition ferromagnetic–antiferromagnetic was found for the first time on baric dependence of relative magnetic susceptibility both at rise and fall of pressure. Temperature dependence of phase transition ferromagnetic–antiferromagnetic is measured from temperature, phase transition ferromagnetic–antuferromagnetic with increase of temperature T=310–334 K moves to low pressures, amplitude of phase transition falls.

Cross magnetic resistance was measured in magnetic field up to H≤5 kOe. Magnetic resistance is observed in magnetic field under pressure in Cd0.7Mn0.3GeAs2. The increase of pressure and magnetic field leads to growth of positive magnetic resistance, and the amplitude of positive magnetic resistance reaches maximum in field H = 5 kOe and P≤1 GPa. Further increase of pressure leads to suppression of positive magnetic resistance. In the region of magnetic phase transition ferromagnetic–antiferromagnetic at P ≅2 GPa, magnetic resistance changes positive sign for negative. Negative magnetic resistance is ≅ 3% at pressure P >4.5 GPa and field H = 5 kOe. To our opinion, at pressures P < 1GPa a considerable contribution in magnetic resistance gives the scattering of  carriers on fluctuations of magnetizing–magnetic resistance is positive. With growth of pressure in magnetic field occur regulating of spins of manganese ions, scattering decreases, and it leads to negative magnetic resistance. Hysteresis of magnetic resistance is found on dependencies Δρxx/ρ(P) at pressure fall. Hysteresis of magnetic resistance, apparently, is a characteristic of anomalous scattering of charge carriers, occurring at transition in magnetic regulated state at forming of ferromagnetic clusters of nano-measuring (ferrons).

The works has been carried out under financial support of program of Presidium of the Russian Academy of Science “Heat physics and mechanics of external energy influences and physics of heavily condensed matter”.

 

Reference

[1] L.G. Khvostantsev, L.P. Vereshagin, A.P. Novikov. High Temp.- High Pressure, 9, 6, 637, (1977).

[2] A.Yu. Mollaev, R.K. Arslanov, L.A. Saypulaeva, S.F. Marenkin. Inorganic Materials, 37, 4, 405, (2001).

[3] V.I. Chechernikov. Magnetic Measurements, MGU, Moscow, 1963.

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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium E, by Akhmedbek Y. Mollaev
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-10 16:08
Revised:   2009-08-13 17:36
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