Thickness dependent magnetic properties of amorphous FeTaC films

Abstract

We report on the study of thickness and temperature dependent magnetic properties of amorphous FeTaC (t = 20–200 nm) thin films prepared on thermally oxidized Si substrate at ambient temperature. Room temperature coercivity remains constant (∼1.5 Oe) for t between 20 and 50 nm, but increases rapidly (>18 Oe) when t > 50 nm. Also, the shape of M-H loop changes from rectangular to flat loop with increasing film thickness; and at larger thicknesses (>50 nm), the central range of constant slope in the flat loop extended largely along with the enlargement of hysteresis around the origin. This is mainly due to the development of perpendicular anisotropy with increasing the film thickness causing a transition from in-plane orientations of the spins to a magnetic stripe domain structure, which degrades the magnetic properties at larger thickness. Low temperature thermomagnetization curves obtained under zero-field-cooled (ZFC) and field-cooled (FC) conditions depicts a bifurcation between ZFC and FC data at larger thickness films. With decreasing t, the bifurcation point shifted to lower temperatures and almost disappeared for t ≤ 50 nm. On the other hand, the high temperature magnetization data reveal a considerable increase in Curie temperature with decreasing film thickness and the magnetic susceptibility critical exponent γ exhibits a thickness dependent behavior. The observed results are discussed on the basis of two-layer model, and the development of perpendicular anisotropy and magnetic disorder with increasing FeTaC film thickness.

Perpendicular Standing Spin Wave and Magnetic Anisotropic Study on Amorphous FeTaC Films

“…The coercivity fields (H C ) for 20 and 50 nm samples are found to be 1.5 and 2 Oe, respectively which is a characteristic feature of soft ferromagnetism. By increasing the film thickness (≥ 100 nm), the M − H clearly shows the transcritical loop manifesting the presence of stress induced perpendicular anisotropy during the film deposition [5]. M S is found to increase from 6125 ± 30 Oe to 7740 ± 40 Oe as the film thickness increases from 20 to 200 nm.…”

“…The amorphous nature of those alloys reduces the number of pinning centers which may lead to the spin transfer torque (STT)-driven domain wall motion along with high tunneling magnetoresistance ratio (TMR) [1]. It has been reported that the addition of 20 % metalloid (in this case 'Ta' and 'C') in Fe based FM metal matrix destroys crystallinity and shows enhanced soft magnetic properties [2], [3], [4], [5], [6]. Furthermore, the soft magnetism in Fe based nanocrystalline alloys arises from two-phase microstructure in which fine nanocrystals are embedded in amorphous matrix, resulting a strong intergranular FM exchange coupling [7].…”

Spin dynamics and frequency dependence of magnetic damping study in soft ferromagnetic FeTaC film with a stripe domain structure

“…14,15 Malinowski et al In this letter, we focus on amorphous FeTaC layer due to its interesting soft ferromagnetic (FM) properties. 17,18 The amorphous soft FM layer reduces the number of pinning centers which may lead to the STT-driven domain wall motion along with high tunneling magnetoresistance ratio (TMR). The transcritical loop along with the stripe domain structure, which are the manifestation of PMA component were reported on FeTaC thin film with thickness of 200 nm.…”

“…The transcritical loop along with the stripe domain structure, which are the manifestation of PMA component were reported on FeTaC thin film with thickness of 200 nm. 18,19 To shed some more light onto its dynamic magnetic properties, we have further studied this film by using ferromagnetic resonance technique. Though the magnetic anisotropy and Gilbert damping have been studied by FMR technique in several magnetic thin films like Heusler alloys, permalloy, soft magnetic materials and multilayered (FM/antiferromagnetic or non-magnetic/FM) magnetic films for magnetic recording, MTJ and TMR reader applications, most of the reports are limited to single frequency due to the measurements in X-band electron-spin-resonance spectrometer where the cavity resonates at particular frequency.…”

“…18 The static and dynamic magnetic properties were explored by using a vector network analyzer (VNA) based homemade micro-strip ferromagnetic resonance (MS-FMR) spectrometer. The micro-strip line which was coupled to VNA and Schottky diode detector (Agilent 8473D) through high frequency coaxial cables was mounted in between the pole pieces of the electromagnet.…”