High Pressure Synthesis and Magnetic Properties of Cubic B20 MnGe and CoGe

Abstract:

Samples of MnGe and CoGe having cubic B20 structure were prepared at high pressure. Magnetic measurements showed that CoGe is a Pauli paramagnet, but MnGe exhibits antiferromagnetic-type ordering below T_N = 175 K. The magnetic susceptibility of MnGe follows a Curie-Weiss law above 300 K with an effective magnetic moment µ_eff = 3.68 µ_B/f.u. and θ_p = + 231 K. The large positive value of θ_p indicates a strong ferromagnetic exchange. The value of the effective moment is close to the free Mn⁴⁺ ion (⁴F_3/2) value 3.87 µ_B/f.u. From measurements of the magnetization of MnGe in fields up to 60 kOe and in the temperature range 2-350 K, we constructed its T-H magnetic phase diagram which is similar to that proposed for MnSi-type compounds with helical magnetic order. Specific heat measurements reveal that the total magnetic entropy of MnGe relative to nonmagnetic CoGe is equal to 3.55 J/mole-K (0.62Rln2).

• Periodical: Solid State Phenomena (Volume 190)
• Pages: 225-228
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.190.225
• Online since: June 2012
• Authors: A.V. Tsvyashchenko, V.A. Sidorov, L.N. Fomicheva, V.N. Krasnorussky, R.A. Sadykov, J.D. Thompson, K. Gofryk, F. Ronning, V.Y. Ivanov
• Keywords: B20 Structure, CoGe, Helimagnet, High-Pressure Synthesis, Magnetization, MnGe, Specific Heat

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