Enhancing High-Frequency Properties of Nanocrystalline Sputtered Fe Thin Films by Using MnIr Underlayer and Oblique Depo
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LETTER
Enhancing High-Frequency Properties of Nanocrystalline Sputtered Fe Thin Films by Using MnIr Underlayer and Oblique Deposition Kh. Gheisari 1
&
C. K. Ong 2
Received: 1 August 2020 / Accepted: 4 November 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this work, the single-layer Fe and the bilayer MnIr/Fe thin films were fabricated on Si (100) substrate using the oblique-angle sputtering technique. The structure and magnetic properties of the as-deposited films were investigated. MnIr biased layer deposited at the normal incidence angle develops an exchange bias field of 5.2 Oe which leads to an increase in the uniaxial anisotropy field of Fe layer from 4.36 to 23.66 Oe and the ferromagnetic resonance frequency from 1.02 to 1.46 GHz. It is also found that the resonance frequency of the bilayer MnIr/Fe rises sharply from 1.46 to 5.05 GHz as the incident angle increases from 0 to 36°. Keywords Exchange bias . Oblique-angle sputtering technique . Magnetic anisotropy . MnIr/Fe film . Ferromagnetic resonance frequency
1 Introduction The exchange bias effect between an antiferromagnet (AF) and ferromagnet (FM) layers has been widely investigated owing to its potential applications in many electronics systems such as magnetic recording, spin-valve sensors, and highfrequency devices [1, 2]. This interesting effect can be explained on the base of the spin alignment in the FM–AFM interface in such a way that in presence of an applied magnetic field, AFM spins tend to align parallel to the direction of FM spins and applied field. When the magnetic field is reversed, due to the interface coupling, a microscopic torque is exerted to the FM spins keeping them in their initial position. Hence, an extra external field will be required to completely reverse the magnetization in the FM layer. Consequently, this effect appeared as a hysteresis loop shift from the origin or as a coercivity enhancement [3, 4]. One advantage of this phenomenon in the magnetic thin films is that it can shift the ferromagnetic resonance frequency * Kh. Gheisari [email protected] 1
Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
2
Center for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, Singapore, Singapore
to the higher frequency region [5–7]. On the other hand, the oblique-angle sputtering as a simple and effective method can enhance the resonance frequency of soft magnetic thin film due to the formation of a high in-plane uniaxial magnetic anisotropy during the deposition process [8–10]. The present work is aimed at preparing the Fe thin film with high resonance frequency using MnIr antiferromagnet sublayer via the oblique-angle sputtering technique. MnIr bias layer has been chosen because of its high Neel temperature and its strong exchange biasing effect [6]. Regarding the literature in this area, no attempts have been made on optimizing resonance frequency of Fe thin films
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