Intrinsic magnetic properties of the iron-rich ThMn₁₂-structure alloys R(Fe₁₁Ti); R=Y, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm and Lu

Abstract

Magnetic properties of the series of ThMn,,-structure intermetallic compounds R(Fe,,Ti) have been determined for rare earths from Nd to Lu plus Y. The highest Curie temperature (607 K) is for R = Gd, and R-Fe exchange interactions are much stronger for light rare earths than for heavy ones. The temperature dependence of the iron sublattice magnetisation and anisotropy are determined for the Y and Lu compounds. Spin reorientation transitions are found as a function of temperature for the rare earths with a negative second-order Stevens coefficient cu,(Nd, Tb, Dy), and a set of crystal-field parameters is derived to account for the transitions in a consistent way. A sharp increase in magnetisation observed for Sm(Fe,,Ti) below 130 K in a field of about 10 T applied perpendicular to the easy direction indicates that J-mixing may be important for Sm3'. Compared with R2Fe,4B, the iron anisotropy in R(Fe,,Ti) is greater, and the rare-earth anisotropy is much weaker at low temperature, with the opposite sign for the rare-earth crystal-field coefficient Azo. The average iron moment is 1.7 pB in R(Fe,,Ti) at 4.2 K; Mossbauer spectra are analysed to yield the average moments on each site. Limits set by the intrinsic magnetic properties on the performance of magnets made from these families of alloys are discussed.

Anomalous behavior of electrical resistivity in NdFe 11 Ti

“…Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses of the annealed sample show the compound was single phase. The lattice parameters obtained for the powder sample, a = 8.584 Å and c = 4.791 Å, are in good agreement with the literature [4].…”

“…Such observations are usually obtained from a precise magnetization measurements performed on single crystals. The peak shown in the magnetization curve of NdFe 11 Ti at 200 K [4] is thought to be due to a spin reorientation transition (SR) from conical to unixal anisotropy, but for a polycrystalline sample this temperature may be extended over a wide temperature range according to the sign of the second anisotropy constant (K 2 ) [4] (i.e. spin reorientation starts from a T SR1 , and completes at T SR2 ).…”

Stress-induced magnetic domain structure in DyFe11Ti compound

“…The RFe 11 Ti intermetallic compounds are now reconsidered as promising materials for permanent magnets with low contents of rare earth materials. This compound has ThMn 12 -type tetragonal crystal structure (space group I4/mmm) and is characterized by reasonably high values of the Curie temperature and of the spontaneous magnetic moment [5][6][7]. DyFe 11 Ti compound has uniaxial magnetic anisotropy at room temperature.…”

“…This compound is characterized by the two spin-reorientation phase transitions (SRT). According to the literature data, SRT temperatures significantly vary: the SRT1 is observed in the temperature range of 98-120 K, SRT2 -214-250 K [5][6][7][8][9][10]. Besides, DyFe 11 Ti compound possess the large magnetostriction [11].…”

Anomalies in magnetoelastic properties of DyFe11.2Nb0.8 compound

“…1 The competing anisotropy contributions from the two sublattices can therefore lead to spin reorientation transitions. However, there exist some inconsistencies in the reported magnetic transitions for Dy(Fe,T) 12 compounds such as spin reorientation and first-order magnetization transition 4,5 -Hu et al 4 suggested that a first-order spin reorientation takes place at T sr1 with a second-order spin reorientation occurring at T sr2 , while Andreev et al 5 reported two consecutive second-order spin reorientations at T sr1 and T sr2 .…”