Thickness Variation Of The Magnetic Anisotropy In DyFe Thin Films Using Magneto-optical Techniques

Abstract

Thickness(nm) 134 100.5 67 53.6 40.2 33.5 26.8 13.4 HK(k0e) 3.50 5.78 5.10 4.92 6.13 7.17 6.35 3.97 Ms(emu/cc) 230 203 178.5 163 140 129 109 69In two previous studies [l, 21, we reported a new investigation of structural dependence of the perpendicular magnetic anisotropy in DyFe and DyFeCo films by preparing different multilayer structures of films with constant thickness (70 nm) and composition (carefully monitored by constant Ms, Tamp and Tcde). The present work continues this study and reports the thickness dependence of the perpendicular magnetic anisotropy in DyFe films having an homogeneous amorphous phase as the thickness is changed from 13.4-134 nm.This series of DyFe films was prepared using a scanning substrate plattem, multi-target, DC magnetron co-sputtering process similar to [l]. Maintaining constant power on each 6" target and constant substrate scanning rate, the sputtering duration was reduced from 20 minutes to 1 minute. Thickness measurements of the series were performed using a Tolansky interferometer. The composition of the films, using EDAX measurements and thermo-magnetic profiles, was found to be DylsFegz. As the thickness of the films was decreased the stable position of the magnetisation was observed to move from out of plane to in-plane. Therefore, anisotropy measurements for samples possessing perpendicular magnetisation were performed using the transverse Ken effect [2,3] whilst samples with in-plane magnetisation were measured using the polar Kerr effect (see Figure 1). In each case the saturation magnetisation Ms was measured separately in a sensitive VSM. The perpendicular magnetic anisotropy (KL) or the in-plane uniaxial anisotropy @Cl) is obtained for each film by assuming coherent rotation of the magnetisation in an applied field Ha as the magnetisation is moved fiom the easy to the hard direction (see [3]). & is the coercivity in the polar Kerr effect measurement for all films. Polarised U polar light '4 TransverseKen Configuration Polar Kerr Configuration e m H. > Figure 1 : MO configurations for Anisotropic measurementsAs the thickness is reduced, the perpendicular magnetic anisotropy also reduces until at a thickness close to 60 nm (see Figure 3) the perpendicular magnetic anisotropy is balanced by the shape effect and the film is effectively isotropic. At this thickness the coercivity normal to the film plane goes to zero. Table 1 shows the measured values as the thickness is decreased. 13w 100, 0 50 IM) 0 50 100 1 50 DyFe Film Thickness (MI) DyFe Film Thickness (nm) Figure 3Figure 2 1 KI (ergkc) lo5 I 7.35 8.46 2.46 2.34 3.06 3.58 2.71 1. IThe reason for the gradual change in the saturation magnetisation as the thickness is decreased is not completely understood and a number of different results relating to thickness effect have been previously reported [4, 51. The sample composition was monitored by careful thermo-magnetic measurements using a cryogenic stage. Tcurie and TCq were found to be 358K and 125K respectively for several thick samples (e.g. 134 and 100.5 nm) so ...

Influence of nanoholes array geometrical parameters on magnetic properties of Dy–Fe antidot thin films

“…This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short-range order[25]. As a result, a more collinear alignment of the distributed magnetic moments of Dy along the out-of-plane direction with film thickness is obtained[39]. It is worth noting that all CTF samples show apositive value of Keff and Keff × t, i.e.…”