Origin of Perpendicular Magnetic Anisotropy in Tb-Fe Amorphous Alloy

Ohta, M.; Yamada, Kazumasa; Satake, Yoshihiko; Fujita, Akira; Fukamichi, K.

doi:10.2320/matertrans.44.2605

Cited by 12 publications

(7 citation statements)

References 19 publications

(34 reference statements)

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“…These structural changes are probably linked to the strains induced in the alloy during film growth and their release with the temperature, possibly favored by their interplay with the magnetoelastic properties of each of the magnetic environments. The importance of anelastic strains in the development of the magnetic anisotropy of these alloys is well known [11,68,69]. In fact, we have observed an irreversible reduction of about 20% in the magnetic anisotropy of our films with annealing temperatures of only 400 K [41].…”

Section: Variation Of the Measured Neodymium Magnetic Momentmentioning

confidence: 55%

Perpendicular magnetic anisotropy in amorphous NdxCo1−x thin films studied by x-ray magnetic circular dichroism

et al. 2017

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The origin of perpendicular magnetic anisotropy (PMA) in amorphous Nd x Co 1−x thin films is investigated using x-ray magnetic circular dichroism (XMCD) spectroscopy at the Co L 2,3 and Nd M 4,5 edges. The magnetic orbital and spin moments of the 3d cobalt and 4f neodymium electrons were measured as a function of the magnetic field orientation, neodymium concentration, and temperature. In all the studied samples, the magnetic anisotropy of the neodymium subnetwork is always oriented perpendicular to the plane, whereas the anisotropy of the orbital moment of cobalt is in the basal plane. The ratio L z /S z of the neodymium 4f orbitals changes with the sample orientation angle, being higher and closer to the atomic expected value at normal orientation and smaller at grazing angles. This result is well explained by assuming that the 4f orbital is distorted by the effect of an anisotropic crystal field when it is magnetized along its hard axis, clearly indicating that the 4f states are not rotationally invariant. The magnetic anisotropy energy associated to the neodymium subnetwork should be proportional to this distortion, which we demonstrate is accessible by applying the XMCD sum rules for the spin and intensity at the Nd M 4,5 edges. The analysis unveils a significant portion of neodymium atoms magnetically uncoupled to cobalt, i.e., paramagnetic, confirming the inhomogeneity of the films and the presence of a highly disordered neodymium rich phase already detected by extended x-ray-absorption fine structure (EXAFS) spectroscopy. The presence of these inhomogeneities is inherent to the evaporation preparation method when the chosen concentration in the alloy is far from its eutectic concentrations. An interesting consequence of the particular way in which cobalt and neodymium segregates in this system is the enhancement of the cobalt spin moment which reaches 1.95 μ B in the sample with the largest segregation.

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Section: Variation Of the Measured Neodymium Magnetic Momentmentioning

confidence: 55%

Perpendicular magnetic anisotropy in amorphous NdxCo1−x thin films studied by x-ray magnetic circular dichroism

et al. 2017

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“…In this regard, a lot of effort has been made to investigate the intrinsic magnetic properties over a wide composition as well as temperature range, and how they are influenced by the growth conditions, like sputtering pressure (Jiang et al, 2010), substrate choice (Na et al, 2003), substrate bias voltage (Alperin et al, 1975), or external strain (Ohta et al, 2003). These research activities were encouraged by improved preparation techniques, which allowed preparing thin films in the thickness range of only some nanometers at reproducible high quality.…”

Section: Hebler Et Al Ferrimagnetic Tb-fe Alloy Thin Filmsmentioning

confidence: 99%

Ferrimagnetic Tb–Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

et al. 2016

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Ferrimagnetic rare earth -transition metal Tb-Fe alloy thin films exhibit a variety of different magnetic properties, which depend strongly on composition and temperature. In this study, first the influence of the film thickness (5-85 nm) on the sample magnetic properties was investigated in a wide composition range between 15 and 38 at.% of Tb. From our results, we find that the compensation point, remanent magnetization, and magnetic anisotropy of the Tb-Fe films depend not only on the composition but also on the thickness of the magnetic film up to a critical thickness of about 20-30 nm. Beyond this critical thickness, only slight changes in magnetic properties are observed. This behavior can be attributed to a growth-induced modification of the microstructure of the amorphous films, which affects the short range order. As a result, a more collinear alignment of the distributed magnetic moments of Tb along the out-of-plane direction with film thickness is obtained. This increasing contribution of the Tb sublattice magnetization to the total sample magnetization is equivalent to a sample becoming richer in Tb and can be referred to as an "effective" composition. Furthermore, the possibility of all-optical switching, where the magnetization orientation of Tb-Fe can be reversed solely by circularly polarized laser pulses, was analyzed for a broad range of compositions and film thicknesses and correlated to the underlying magnetic properties.

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“…Thin films of an amorphous RE-TM ferrimagnet have been often reported to exhibit PMA, possibly from the interfacial strain on the ferrimagnetic layer involving multiple mechanisms associated with magnetostriction, [36] dipolar effects, [37] and anisotropic atomic-pairs correlations. [38][39][40] In addition, the MA of the ferrimagnetic layer was found to be sensitive to the growth conditions (e.g., growth of the layer under external strain [41] and the presence of Ta underlayer [22] ) as well as the post-annealing procedures. [42] Ueda et al [22] reported that the threshold thickness of the RE-TM ferrimagnetic layer for the transition of MA from IMA to PMA can vary depending on the existence of the Ta underlayer.…”

Section: Tma In Gd/co Multilayers For In-plane Symmetry Breakingmentioning

confidence: 99%

Field‐Free Switching of Magnetization by Tilting the Perpendicular Magnetic Anisotropy of Gd/Co Multilayers

Kim

Moon

Tran

et al. 2022

Adv Funct Materials

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Efficient current‐induced switching of perpendicular magnetization is an essential task in spintronics for realizing high‐performance information processing and for storage device application. However, the spin‐orbit torque (SOT) by injection of in‐plane polarized spins cannot deterministically switch the magnetization of ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) without an additionally applied in‐plane external magnetic field to break the symmetry of the PMA. Considering the difficulties of applying the magnetic field to the localized area only within a device structure, it is essential to contrive a facile field‐free SOT switching mechanism. Here, deterministic field‐free SOT switching of perpendicular magnetization is achieved in amorphous and ferrimagnetic Gd/Co multilayers accompanied by a tilted magnetic anisotropy axis. This tilted anisotropy originates from the combined contributions of many internal anisotropies in different orientations from the multilayers and is shown to be controllable. It is expected that the introduction of controlled tilted anisotropy into Gd/Co multilayers over the entire film surface in the present study can be extended to the development of wafer‐scale technologies for the spintronics memory and logic devices.

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Origin of Perpendicular Magnetic Anisotropy in Tb-Fe Amorphous Alloy

Cited by 12 publications

References 19 publications

Perpendicular magnetic anisotropy in amorphous NdxCo1−x thin films studied by x-ray magnetic circular dichroism

Perpendicular magnetic anisotropy in amorphous NdxCo1−x thin films studied by x-ray magnetic circular dichroism

Ferrimagnetic Tb–Fe Alloy Thin Films: Composition and Thickness Dependence of Magnetic Properties and All-Optical Switching

Field‐Free Switching of Magnetization by Tilting the Perpendicular Magnetic Anisotropy of Gd/Co Multilayers

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