Сибирский федеральный университет

Тип публикации: статья из журнала

Год издания: 2008

Идентификатор DOI: 10.1088/0953-8984/20/44/445214

Ключевые слова: Antiferromagnetism, Crystallography, Entropy, Lead alloys, Magnetic materials, Magnetism, Manganese, Manganese compounds, Powders, Single crystals, Specific heat, Spin dynamics, Antiferromagnetic orders, Charge localizations, Entropy losses, Excess heat capacities, Experimental datums, Heat capacities, Magnetic contributions, Magnetic orders, Magnetic states, Magnetic subsystems, Magnetic transitions, Manganese oxides, Nonmagnetic, Spin systems, Temperature curves, Temperature dependences, Temperature intervals, Temperature ranges, Manganese alloys

Аннотация: We present the results of a heat capacity study of Pb(3)Mn(7)O(15) single crystals with approximately equal concentrations of Mn(3+) and Mn(4+) ions. In the temperature interval between 210 and 260 K, an excess heat capacity of nonmagnetic origin, most likely associated with the process of charge localization, has been observed. Also, three pronounced anomalies corresponding to the changes in a magnetic subsystem of the crystal have been observed in the temperature dependence of the heat capacity. A broad hump near 150 K is related to the formation of a short-range magnetic order. This process of short-range ordering is rather prominent, considering the appreciable value of the entropy loss accompanying the change in the magnetic state. A clear lambda-shaped peak at 70 K marks the onset of a long-range antiferromagnetic order. Another anomalous contribution to the heat capacity of magnetic origin has been revealed at temperatures below 20 K. This contribution is associated with a magnetic transition of an unknown nature, which is also clearly evident in magnetization versus temperature curves. The total magnetic contribution to the entropy deduced from the actual experimental data over the entire temperature range is much smaller than is expected for a completely ordered Mn spin system in the crystal. We suggest several possible reasons that may account for this `missing' entropy.

Журнал: JOURNAL OF PHYSICS-CONDENSED MATTER

Выпуск журнала: Vol. 20, Is. 44

ISSN журнала: 09538984

Место издания: BRISTOL

Издатель: IOP PUBLISHING LTD

• Volkov N.V. (RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia; Siberian Fed Univ, Dept Phys, Krasnoyarsk 660041, Russia)
• Sablina K.A. (RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia)
• Eremin E.V. (RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia)
• Boeni P. (Tech Univ Munich, Dept Phys E21, D-85747 Garching, Germany)
• Shah V.R. (Indiana Univ, Dept Phys, Bloomington, IN 47405 USA)
• Flerov I.N. (RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia; Siberian Fed Univ, Dept Phys, Krasnoyarsk 660041, Russia)
• Kartashev A. (RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia)
• Rasch J.C.E. (Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France; Swiss Fed Inst Technol, Neutron Scattering Lab, CH-5232 Villigen, Switzerland; Paul Scherrer Inst, CH-5232 Villigen, Switzerland)
• Boehm M. (Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France)
• Schefer J. (Swiss Fed Inst Technol, Neutron Scattering Lab, CH-5232 Villigen, Switzerland; Paul Scherrer Inst, CH-5232 Villigen, Switzerland)

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