Antiferromagnetic‐to‐ferromagnetic transition induced by aluminum in the Ti(Fe_1−xAl_x)₂ intermetallic compounds: a ⁵⁷Fe Mössbauer spectroscopy study

Abstract

PACS 71.20. Lp, 75.25.+ z, 76.80.+ y Mössbauer spectroscopy has been used to investigate the hyperfine field distributions and the local spin configurations of Fe atoms in the magnetically ordered Ti(Fe 1-x Al x ) 2 compounds. The evolution of the spin arrangement of the Fe atoms was observed over the concentration range 0 ≤ x ≤ 0.25 at 5 K. The Al impurity suppresses the ferromagnetic exchange in the Fe(6h) layers and simultaneously provides the conditions for a transition of the Fe(2a) atoms, which are nonmagnetic in the TiFe 2 compound, to the states with nonzero magnetic moment. The magnetic behavior of the Fe(2a) atoms is the key factor governing the anti-to ferromagnetic transition in the Ti(Fe 1-x Al x ) 2 compounds. The magnetic ordering temperatures of the Ti(Fe 1-x Al x ) 2 compounds were determined. In addition, the parameters of the electric-field gradient in TiFe 2 as well as the relationship between the value of the magnetic moment of the Fe atom and the type of atomic configuration were discussed.

Ferromagnetic-to-antiferromagnetic transition in (Hf1−xTix)Fe2 intermetallic compounds induced by geometrical frustration of the Fe(2a) sites

“…The concentration dependence of the /QSHS provides information about the rotation of the Fe(6h) magnetic moments on the average. In the HfFe 2 compound with a collinear FM structure, QSH is equal to +0.053(5) mm/s, suggesting that the magnetic moments are aligned parallel to the hexagonal c-axis [12,15]. In the (Hf 1Àx Ti x )Fe 2 compounds, as the Ti concentration increases, the /QSH(6h)S value increases rapidly.…”

“…For TiFe 2 , the spectrum consists of the magnetic subspectrum (6h sites, B hf ¼ 9.70(3) T) and quadrupole doublet (nonmagnetic 2a sites). The parameters of the hyperfine interactions for 57 Fe in TiFe 2 have been previously considered in detail [15]. In particular, it was shown that the principal component of the EFG tensor lies in the basal plane.…”

“…The rotation of the Fe(6h) magnetic moments would be reflected by changes in the QSH value which depends on the polar and azimuth angles determining the orientation of the magnetic moments in the coordinate system of the EFG tensor axes [15]. Obviously, the orientation of magnetic moments will be dependent on the local Ti concentration.…”