Structure, spin reorientation and Mössbauer effect studies of Tb0.3Dy0.7(Fe1−x Alx)1.95 alloys

Abstract

The effect of Al substitution for Fe on crystal structure, magnetostriction and spontaneous magnetostriction, anisotropy and spin reorientation of a series of polycrystalline Tb 0.3 Dy 0.7 (Fe 1−x Al x ) 1.95 alloys (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35) at room temperature and 77 K was investigated systematically. It was found that the primary phase of Tb 0.3 Dy 0.7 (Fe 1−x Al x ) 1.95 is the MgCu 2 -type cubic Laves phase structure when x < 0.4 and the lattice constant a of Tb 0.3 Dy 0.7 (Fe 1−x Al x ) 1.95 increases approximately and monotonically with the increase of x. The substitution of Al leads to the fact that the magnetostriction λ inceases slightly in a low magnetic field (H ≤ 40 kA/m), but decreases sharply and is easily close to saturation in a high applied field as x increases, showing that a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. It was also found that the spontaneous magnetostriction λ 111 decreases greatly with x increasing. The analysis of the Mössbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the changes of composition and temperature, namely spin reorientation. A small amount of non-magnetic phase exists for x = 0.15 in Tb 0.3 Dy 0.7 (Fe 1−x Al x ) 1.95 alloys and the alloys become paramagnetic for x > 0.15 at room temperture, but at 77 K the alloys still remain magnetic phase even for x = 0.2. At room temperature and 77 K, the hyperfine field decreases and the isomer shifts increase with Al concentration increasing.

Mössbauer effect studies of Tb0.27Dy0.73(Fe1−x Co x )2 intermetallics at 295 K

“…This formula is used to follow the experimental points and is obtained by a least squares fitting procedure. The border line values of the studied series coincide well with the existing literature data (open points) [22][23][24][25][26][27]. The observed convex deviation a(x) from Vegard's rule, i.e.…”

Magnetics, Magetostriction, and Spin Reorientation of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 Alloys with Substitution of Fe by Al

“…Al substitution effect completely destroys the spin exchange coupling between Fe-Fe, R-Fe and R-R when x>0.25 so that Tb 0.3 Dy 0.7-x Pr x (Fe 0.9 Al 0.1 ) 1.95 alloys are of paramagnetism, in which magnetization increases linearly with the external magnetic field. Comparing to the results in our previous investigations [4,10] , we found that Pr substitution improve the Al content of the ferromagnetic alloys. Similarly, Fig.2 indicates that the magnetization is saturated more easily, implying magnetocrystalline anisotropy reduces in the Tb 0.3 Dy 0.7-x Pr x (Fe 0.9 Al 0.1 ) 1.95 alloys.…”

“…Judging by these research reports, Al is regarded as an ideal substitution for Fe. The application properties of Tb 0.3 Dy 0.7 (Fe 0.9 Al 0.1 ) 1.95 alloys turn out excellent [5][6][7][8][9][10][11] because the addition of Al to Fe increases resistivity and ductility and decreases anisotropy, but its saturated magnetostriction greatly decreases. On the basis of retaining the good application properties, we anticipate that substitution of other elements for Tb or Dy enhances the saturated magnetostriction of Tb 0.3 Dy 0.7 (Fe 0.9 Al 0.1 ) 1.95 alloys.…”

“…Furthermore, the sign of magnetostriction of TbFe 2 , DyFe 2 and PrFe 2 is the same, but the sign of anisotropy of TbFe 2 is reversible with that of DyFe 2 and PrFe 2 . Clark et al [10] investigated the magnetocrystalline anisotropy of RFe 2 series with the results that the compensating multi-element composition of RFe 2 (R is the two or three elements) retains large magnetostriction and decreasing magnetocrystalline anisotropic, which is composed of these RFe 2 with the same magnetostriction sign and opposite magnetocrystalline anisotropy. Lou [7] and Zhan [8] groups investigated the effect of Pr substitution for Dy on the anisotropy, magnetostriction and magnetism of the various RFe 2 alloys.…”

Hyperfine interactions and electronic band structure in compounds

“…. , 0.9 and 1.0) with a cubic, Fd3m, MgCu 2 -type (C15) crystal structure have been previously partially studied elsewhere [18][19][20][21][22][23][24]. The unit cell parameter, for complete data of the series, described by the following numerical formula: a(x) = (−0.104x 2 − 0.029x + 7.337) Å decreases softly non-linearly with cobalt content x [25].…”