Magnetic properties of RMn2Ge2 compounds (R=La, Ce, Pr, Nd, Cd, Tb, Dy, Ho, Er, and Th)

Abstract

Magnetic properties RMn2Ge2 compounds where R is La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Th have been investigated from 4.2 to 500 K. LaMn2Ge2, CeMn2Ge2, PrMn2Ge2, and NdMn2Ge2 are ferromagnetic with Curie temperatures of 306, 316, 334, and 334 K, respectively. The heavy rare-earth compounds do not order ferromagnetically until low temperatures. GdMn2Ge2 shows a sharp magnetic transition at 97 K both in the magnetization-vs-temperature and resistivity-vs-temperature data. For this compound, it is proposed that above 97 K the Mn moments order antiferromagnetically among themselves while the Gd moments are disordered. Below 97 K the Mn moments couple ferromagnetically with each other but are opposed to the ordered Gd sublattice. Magnetic moment obtained at 4.2 K can be explained for all the compounds on the basis of an antiferromagnetic coupling between Mn and rare-earth spins.

Ferromagnetic feature from Mn near room temperature in the fine particles of GdMn 2 Ge 2 and TbMn 2 Ge 2

“…With this primary motivation, we synthesized fine particles which are less than 1 µm in size for Gd and Tb members and studied the magnetization behavior. In the bulk form, the antiferromagnetic coupling among ferromagnetic Mn layers in GdMn 2 Ge 2 sets in below 365 K and there is a first-order transition at about 95 K to ferrimagnetism with decreasing temperature following simultaneous Gd sublattice ordering [10,14,15,16] and ferromagnetic alignment of all Mn planes. The corresponding T N for TbMn 2 Ge 2 has been reported to be in the range 400 -450 K, with the first-order ferromagnetic transition setting in at about 95 K [5,17,18,19].…”

Thermomagnetic history effects inSmMn2Ge2

“…Various kinds of magnetic phase transitions, viz., paramagnetic (PM) to ferromagnetic (FM), PM to antiferromagnetic (AFM), FM to AFM, AFM to FM or ferrimagnetic state (at low temperature, T) can be observed in different compounds belonging to this class of materials. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] The unit cell in these compounds, consists of layered structure ..-Mn-Mn-R-Ge(or Si)-R-Mn-Mn-.. stacked along the c-axis. Within the ab-plane, the Mn-Mn interaction is FM-like for all temperatures below the highest ordering temperature.…”

XRD, AC susceptibility and DSC studies of PrMn 2–x Ni x Ge 2 compounds

“…In such compounds, there exists a transition from anti-ferromagnetic to ferromagnetic state induced by temperature and/or magnetic field, giant magnetoresistance at metamagnetic transition, reentrant ferromagnetism and canted ferromagnetic structure [3][4][5][6][7]. It is well known that the most of the compounds carry no magnetic moment on the transition metal (T), while the Mn sublattice orders magnetically [8].…”