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We demonstrate the possibility to tune the saturation magnetization, coercivity, and uniaxial in-plane anisotropy constant in amorphous bilayers and multilayers of Co85(Al70Zr30)15 and Sm11Co82Ti7 through the interface density. From magnetometry and x-ray circular dichroism (XMCD) measurements, we conclude that the easy-axis coercivity 𝜇0𝐻𝑐 increases four times when the number of bilayer repetitions, 𝑁, increases from 1 to 10 within a constant total sample thickness of 20 nm. At the same time, the anisotropy constant 𝐾𝑢 also increases by a factor four, whereas the saturation magnetization 𝑀𝑠 decreases slightly. The Co spin and orbital moments, 𝑚𝑠 and 𝑚𝑙, are found to be approximately constant within the sample series. The average total Co moment is only 0.8–0.9 𝜇𝐵/atom, but the 𝑚𝑙/𝑚𝑠 ratio is strongly enhanced compared to pure Co. Magnetization curves extracted from XMCD measurements show that the Co and Sm moments are ferromagnetically coupled for all samples.

Magnetometry and first-principles density functional theory-based calculations were used to investigate the concentration dependence of magnetic properties of amorphous CoxZr100-x alloys. A linear increase in saturation magnetization (Ms) is observed in both the experiments and calculations. Samples with Co content of at least 62 at.% are inferred to be ferromagnetic at 5 K. The experimentally determined ordering temperature is found to scale quadratically with Co concentration indicating a complex interplay between local structural motifs and magnetic parameters such as exchange interaction and anisotropy.

Better understanding of the nature of magnetic coupling in soft/hard nanocomposites paves the way for tailored exchange-spring magnets. We have investigated a series of amorphous magnetic thin films and trilayers of magnetically soft Co85(Al70Zr30)15 and magnetically hard Sm12Co81Ti7, produced with DC magnetron sputtering. The overall magnetic properties of the trilayers were investigated with focus on the effects of layer configuration and thicknesses on coercivity, originating from the Sm12Co81Ti7 phase, and uniaxial in-plane anisotropy induced from the Co85(Al70Zr30)15 phase. In addition, we found that the thermal stability of a 20 nm Sm12Co81Ti7 layer was significantly increased if surrounded by two 10 nm Co85(Al70Zr30)15 layers in a trilayer structure.

Alloys of Mn55Al45C2 with additions of VC nano-particles have been synthesized and their properties evaluated. The Mn55Al45C2(VC)(x) (x=0.25, 0.5 and 1) alloys have been prepared by induction melting resulting in a high content of the ferromagnetic tau -phase (>94 wt.%). Powder X-ray diffraction indicates that nano-VC can be dissolved in the alloy matrix up to 1 at.%. On the other side, metallography investigations by scanning electron microscopy and scanning transmission electron microscope show inclusions of the nanosized additives in the microstructure. The effect of nano-VC on the grain and twin boundaries has been studied by electron backscattering diffraction. The magnetization has been measured by magnetometry up to 9 T while the domain structure has been studied using both magnetic force microscopy as well as Kerr-microscopy. For nano-VC contents above 0.25 at.%, a clear increase of the coercive force is observed, from 57 to 71 kA/m. The optimum appears to be for 0.5 at.% nano-VC which shows a 25% increase in coercive force without losing any saturation magnetization. This independent increase in coercivity is believed to originate from the nano-VC reducing the overall magnetic domain size. Overall, we observe that addition of nano-VC could be an interesting route to increase the coercive force of MnAl, without sacrificing saturation magnetization.

Using a combination of extended X-ray absorption fine structure measurements, stochastic quenching (SQ) calculations and Voronoi tessellation analysis, the local atomic environments in thin films of amorphous Sm_xCo_1−x (x= 0.10, 0.22 and 0.35) are investigated and also compared with crystalline stoichiometric Sm–Co alloys of similar compositions. It is found that the variations in local environment around Co atoms in the amorphous films increase with increasing x and that none of the films exhibit any pronounced short-range order around the Sm atoms. There are, however, signs of clustering of Sm atoms in the SQ-generated simulated amorphous materials. Furthermore, good agreement is observed between experimentally obtained parameters, e.g., interatomic distances and coordination numbers, and those extracted from the simulated alloys. This is a strong indication that SQ provides a powerful route to reliable local structure information for amorphous rare earth–transition metal alloys and that it could be used for designing materials with properties that meet the demands of specific applications.

Amorphous TbxCo100-x magnetic alloys exhibit a list of intriguing properties, such as perpendicular magnetic anisotropy, high magneto-optical activity, and magnetization switching using ultrashort optical pulses. Varying the Tb:Co ratio in these alloys allows for tuning properties such as the saturation magnetic moment, coercive field, and the performance of light-induced magnetization switching. In this paper, we investigate the magnetic, optical, and magneto-optical properties of various TbxCo100-x thin-film alloy compositions. We report on the effect the choice of different seeding layers has on the structural and magnetic properties of TbxCo100-x layers. We also demonstrate that for a range of alloys, deposited on fused silica substrates, with Tb content of 24-30 at. %, helicity-dependent all-optical switching of magnetization can be achieved, albeit in a multishot framework. We explain this property to arise from the helicity-dependent laser-induced magnetization on the Co sublattice due to the inverse Faraday effect. Our paper provides an insight into material aspects for future potential hybrid magnetoplasmonic TbCo-based architectures.

Electrification of vehicles and renewable energy is increasing the demand for permanent magnets, but the cost and scarcity of rare-earth metals is an obstacle. Creating nanocomposites of rigidly exchange-coupled hard and soft magnets, for which the magnetization reversal occurs as in a single magnetic-phase material, is a promising route toward rare-earth-lean permanent magnets with high energy products. The hard/soft exchange coupling is, however, often reduced due to rough interfaces and structural defects, resulting in exchange-spring behavior rather than rigid exchange coupling. Here, it is shown that artificially sandwiched hard and soft amorphous magnets produced by magnetron sputtering exhibit smooth interfaces, and the first order reversal curve (FORC) technique is used to show that the hard and the soft phases are rigidly exchange coupled. Micromagnetic simulations, using a random-anisotropy model, are used to predict the thickness limit of the rigid exchange coupling. A great advantage of amorphous hard/soft composites is the possibility to obtain a wide range of magnetic properties by finely tuning the composition of the individual phases.

We report on a detailed investigation of structural and magnetic properties of thin CoFeZr films, produced by combinatorial cosputtering, with compositions in the ranges 30–85 at.% Co, 12–63 at.% Fe, and 4–8 at.% Zr. Extended x-ray absorption fine structure and x-ray diffraction measurements reveal that alloys with a Zr content below 5 at.% are polycrystalline with a bcc structure, while an amorphous morphology is stabilized at Zr contents above 6 at.%. All samples display a growth-induced in-plane uniaxial anisotropy, which is closely related to the Zr concentration gradients across the wafers. A model for the angular dependence of the reduced remanence, including a Gaussian distribution of easy/hard anisotropy axes, is presented and successfully used to fit the data for all samples. The magnetic moments of the polycrystalline films approximately follow the Slater-Pauling curve, and the magnetic moments of the amorphous films follow a similar trend, but with about 20 % lower values. X-ray magnetic circular dichroism measurements show, for the amorphous films, that the Co moments are virtually constant at 1.7(2)μB/atom.

Sputter deposited symmetric multilayers of (n Fe)/(n Ni), with individual thicknesses from n = 4 to n = 48 monolayers (ML), were deposited on epitaxial Cu/Si(001), and their microstructural evolution and magnetic properties versus n have been studied. Elemental layering can be seen with transmission electron microscopy down to n = 4 ML layer thickness, although an intermixed region characterized by a finite interface width is found to be present. This width is composed of the interface roughness as well as the interdiffusion between layers, but the relative contributions from these two sources could not be concluded by the techniques used. The measured elemental layering and X-ray reflectivity (XRR) give an upper limit to the interface width which must be smaller than the thinnest layers, 4 ML. Electron energy loss spectroscopy (EELS), depth profiling X-ray photoelectron spectroscopy (XPS) and also XRR reveal that Fe has a higher tendency to mix with Ni than vice versa. XPS does not have the resolution to measure this thin elemental layering: composition variations for n = 8 ML which are clearly seen by EELS are barely resolved by XPS. The structure was determined by X-ray diffraction, and an epitaxial fcc (001) structure is found to be maintained throughout the multilayers up to n less than or similar to 8 ML. For larger n values, relaxation starts by Fe-fcc(001) layers changing into Fe-bcc(110), which is then followed by Ni-fcc(001) changing from (001) to (111) orientation along the growth direction. A decreased total measured magnetic moment for the fully epitaxial multilayers can be explained by the fcc Fe layers being partly anti-ferromagnetic, whereas the relaxed multilayers exhibit the expected magnetic properties of (bcc Fe) +(fcc Ni).

Fe₆₅Co₃₅ thin films have been deposited on SiO₂ substrates using sputtering technique with different choices of seed layer; Ru, Ni_82.5Fe_17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni_82.5Fe_17.5 and Rh. Adding these seed layers, the coercivity of the Fe₆₅Co₃₅ films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10^-3 and 4.5X10^-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10^-3 and 4.0X10^-3 for annealed samples.