Evolution of the structural and magnetic properties of sputtered TbxFe73Ga27-x (7 at.% ≤ x ≤ 11 at.%) thin films upon the increase of Tb content

Abstract

a b s t r a c tTb x Fe 73 Ga 27-x (7 at.% x 11 at.%) ternary alloys have been obtained by cosputtering from Tb 33 Fe 67 and Fe 72 Ga 28 targets. In contrast with other TbeFeeGa compounds that consist of just one structural phase, the diffraction pattern of the Tb 7 Fe 73 Ga 20 shows the presence of two different phases related to binary Tb eFe and FeeGa alloys. This microstructure evolves as the Tb content is increased, and for a Tb of 11 at.% X-ray diffractometry only evidences the presence of a phase close to the TbFe 2 . Although none of the studied samples show perpendicular magnetic anisotropy, there is a significant component of the magnetization perpendicular to the sample plane. The increase of the Tb content on the compounds from 7 at.% to 11 at.% enhances this component most probably due to the shift of the microstructure towards one similar to the TbFe 2 .

Correlation between local structure and magnetic behavior in co-sputtered TbxFe73Ga27−x (7 ≤ x ≤ 11) thin films

“…This peak is shifted towards lower diffraction angles reflecting the increase of the lattice parameter because of the introduction of Ga in the bcc Fe matrix. For that reason, XRD reveals the presence of Fe-Ga alloys when the detected diffraction peaks of the Fe-bcc structure are shifted to account for this increase of lattice parameter as we have previously reported in reference [23]. Apart from this, it is clearly observed a diffraction peak associated with the TbFe 2 in that same reference.…”

“…In them, the progressive decrease of this parameter for increasing Tb contents points to a higher segregation of Tb to form TbFe 2 , as already pointed out by the diffraction studies [23]. In fact, the development of a more segregated TbFe 2 phase should be the reason for the sharpening of the white line in the XANES upon the increase of Tb [31].…”

“…In particular, λ s shows an increase of  250 % in (110)-textured polycrystalline alloys doped with a 0.3 at.% of Tb [16]. The second explored compositional range has been Tb y Fe 100-x-y Ga x alloys with y between 7 and 11 at.% and x from 13 to 20 at.% obtained by co-sputtering [21][22][23][24], i.e. higher Tb contents than in other works.…”

“…Apart from this, it is clearly observed a diffraction peak associated with the TbFe 2 in that same reference. The diffraction peak related to Fe-Ga shows a decrease of its intensity as the Tb content increases along the studied range, whereas the peak related to TbFe 2 exhibits the opposite behavior [23]. This phenomenon is accompanied by an enhancement of the out-of-plane component of the magnetization.…”

“…To obtain samples with different compositions, we have fixed a DC power of 90 W in the Fe 72 Ga 28 being modified the DC power between 50 and 90 W in the Tb 33 Fe 67 target. In this way, we have managed to obtain the following alloys: [23]. We have also grown binary Fe-Ga and Tb-Fe layers for further comparisons.…”