Magnetic and crystallographic properties of SmMn/sub 6-x/Fe/sub x/Ge/sub 6/ intermetallics

Abstract

The magnetic and crystallographic properties of induction-melted SmMn 6 Fe Ge 6 compounds, where is 0, 0.5, 1.0, and 1.5, have been studied using X-ray diffraction and bulk magnetic measurements between 30 and 490K. All of the samples crystallized in the YCo 6 Ge 6 -type structure with the space group P6/mmm. A small amount, less than 9 mol %, of Sm(MnFe) 2 Ge 2 was present as an impurity in all samples. The unit cell volume decreases with increasing iron content at an average rate of 2.4% per substituted atom at room temperature. The and lattice parameters decrease at an average rate of 1.1 and 0.1% per substituted atom at room temperature, respectively. The magnetic properties deteriorate rapidly as the iron concentration increases beyond = 0 5. Magnetic behavior of SmMn 5 Fe 1 Ge 6 and SmMn 4 5 Fe 1 5 Ge 6 is indicative of antiferromagnetic or ferrimagnetic coupling. According to X-ray diffraction patterns of magnetically aligned powders, the easy direction of magnetization at room temperature for all of the samples lies close to the basal plane of the unit cell.Index Terms-Exchange interaction, magnetic coupling, rareearth and transition metal intermetallics, SQUID bulk magnetic measurements, X-ray.

The relationship between magnetic interactions and near neighbor interatomic distances in the transition metal sublattice of R(Mn/Fe)6A6 (R=Nd or Sm, A=Ge or Sn)

“…1 and 2, the magnetic properties of SmMn 6Ϫx Fe x Ge 6 deteriorate rapidly when the iron content exceeds xϭ0.5. 15 In the case of NdMn 6Ϫx Fe x Ge 6 , the same level of deterioration in magnetic properties appears to start at a slightly higher iron content, near xϭ1. 16 Consequently, substituting iron for manganese in Nd/SmMn 6Ϫx Fe x Ge 6 seems to break down the ferromagnetic coupling within the transition sublattice.…”

“…1 and 2͒. 15,16 These observations indicate that the addition of iron strengthens the magnetic exchange interactions within the lattice. Hence, one can infer that iron and manganese magnetic moments interact ferromagnetically in the stannides.…”

“…The magnetic states noted inTable IIhave been assigned based on the M -T and M -H data mentioned above and the magnetic structures determined from neutron diffraction measurements 15,16. …”

Crystal Structure and Magnetic Properties of HfFe6Ge6-Type ErMn6–xCoxGe6 (x = 0–1.45) Alloys

“…At T C ∼T t stage, magnetization increases again at T C ≈ 250 K; with decreasing temperature, a second peak in the temperature dependence of magnetization at about T t . T t stands for spin reorientation temperature, ,,, which is caused by the transition metal Mn with rare earth Er at low temperatures. , To be precise, this only partial spin reorientation arises through the competition between negative R–Mn and Mn–Mn (the same layer) interactions in the Mn–R–Mn slab owing to a modification of their relative strengths . According to neutron diffraction, the magnetic moment of R is reverse parallel to the Mn magnetic moment, and the magnetic moments between Mn and Mn (the same layer) are in the same direction, , as shown in Figure c,d.…”

“…The ErMn 6 Ge 6 systems are of interest for their magnetic properties with at least two ordering temperatures; the compound has an antiferromagnetic order near 470 K and a second jump near 100 K. ,, In the past, the major attention of RMn 6 Ge 6 systems have been focused on the investigation of their crystallographic, magnetic, and electronic structures, − and the GMR effect is related to the magnetic transition, which can be achieved by adjusting the interaction of Mn–Mn and R–Mn sublattices. The RMn 6 Ge 6 systems consist of Mn–(R, Ge)–Mn and Mn–Ge–Ge–Ge–Mn slabs that are alternately (−Mn–(R,Ge)–Mn–Ge–Ge–Ge–Mn−) stacked along the c -axis; the coupling between the Mn moments in a layer is of the ferromagnetic (FM) type, whereas the coupling between Mn moments in adjacent layers is of the antiferromagnetic type, and it can be significantly changed by appropriately selecting different elements to replace Mn sites. − …”