Magnetic structures and magnetic phase diagram of Nd{sub x}Tb{sub 1{minus}x}Mn{sub 2}Ge{sub 2}
- Departamento de Fisica de la Materia Condensada and Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza and Consejo Superior de Investigaciones Cientificas, 50009 Zaragoza (Spain)
- Institut Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex 9 (France)
The various magnetic structures and magnetic phase transitions in the series Nd{sub x}Tb{sub 1{minus}x}Mn{sub 2}Ge{sub 2} have been thoroughly studied by means of macroscopic magnetic and thermal measurements (such as magnetization, ac initial magnetic susceptibility and linear thermal expansion) and microscopic neutron-diffraction experiments. As a result, the magnetic phase diagram has been determined over the whole temperature range. Large changes in the local Mn magnetic moments (e.g., {Delta}{mu}{sub Mn}/{mu}{sub Mn}{approx}16{percent} in TbMn{sub 2}Ge{sub 2}) have been detected at the magnetic phase transitions observed at low temperatures, {approx}100{endash}140 K, in the x=0{endash}0.4 alloys. This variation, together with the appearance of magnetic ordering in the rare-earth sublattice, has been related to the volume anomalies found (e.g., {Delta}V/V{approx}0.3{percent} in TbMn{sub 2}Ge{sub 2}). A new magnetic structure of the Mn sublattice in the RMn{sub 2}X{sub 2} (R=rare earth, X=Si, Ge) family has been found in Nd{sub 0.4}Tb{sub 0.6}Mn{sub 2}Ge{sub 2} (140K{lt}T{lt}350 K) where two antiferromagnetic commensurate components within the (001) plane coexist with a ferromagnetic component along the c axis. The peculiar layered structure of the RMn{sub 2}Ge{sub 2} compounds favors a cancellation of the molecular field at the rare-earth sites in the case of antiferromagnetic arrangements of the Mn sublattice, effectively isolating the R atoms and making a paramagnetic behavior of these possible despite the presence of long-range order. The existence of a ferromagnetic component in the Mn sublattice has been concluded to be indispensable to allow the ordering of the rare-earth magnetic moments. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 496759
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 55, Issue 18; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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