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It has been possible to grow single crystal Laves phase DyFe2/YFe2 superlattice samples with a (110) growth direction using molecular beam epitaxial techniques. It is concluded that the magnetization loop is almost totally determined by the magnetic exchange springs found in the soft YFe2 layers.

Spin-torque driven ferromagnetic resonance (ST-FMR) is used for studying the magnetic excitations in Co/Ni synthetic layers confined in nanojunctions. The effect of both dipolar fields acting on the Co/Ni layer emanating from other magnetic layers in the device and finite size effects on the spin wave spectrum are examined.

Room-temperature ferromagnetic resonance (FMR) studies of polycrystalline films are presented as a function of Co layer thickness grown by evaporation and magnetron sputtering. Calculation of the spin-mixing conductance at Co/Cu interface showed smaller conductance for evaporated films with Pt layer of 1-5 nm than for sputtered films that have a Pt layer of 5nm.

We present a ferromagnetic resonance (FMR) study of the effect of helium ion irradiation on the magnetic anisotropy, the linewidth and the Gilbert damping of a Co/Ni multilayer coupled to Co/Pd bilayers. The perpendicular magnetic anisotropy decreases linearly with He ion fluence, leading to a transition to in-plane magnetization at a critical fluence of 5×1014 ions/cm2. We find that the damping is nearly independent of fluence but the FMR linewidth at fixed frequency has a maximum near the critical fluence, indicating that the inhomogeneous broadening of the FMR line is a nonmonotonic function of the He ion fluence. Based on an analysis of the angular dependence of the FMR linewidth, the inhomogeneous broadening is associated with spatial variations in the magnitude of the perpendicular magnetic anisotropy. These results demonstrate that ion irradiation may be used to systematically modify the magnetic anisotropy and distribution of magnetic anisotropy parameters of Co/Pd/Co/Ni multilayers for applications and basic physics studies. [ABSTRACT FROM AUTHOR]

Ferromagnetic resonance has been used to study the magnetic properties and magnetization dynamics of polycrystalline Fe1-xVx alloy films with 0<=x<0.7. Films were produced by cosputtering from separate Fe and V targets, leading to a composition gradient across a Si substrate. Ferromagnetic resonance studies were conducted at room temperature with a broadband coplanar waveguide at frequencies up to 50 GHz using the flip-chip method. The effective demagnetization field 4πMeff and the Gilbert damping parameter α have been determined as a function of V concentration. The results are compared to those of epitaxial FeV films. [ABSTRACT FROM AUTHOR]

The Stoner -- Wohlfarth model has proved reasonably successful in describing the coercivities of antiferromagnetically coupled DyFe[SUB2]/Yfe[SUB2] hard/soft superlattices in the absence of magnetic exchange springs. In particular, the coercivity rises sharply as the net magnetic moment of the superlattice approaches zero. However the situation becomes more complicated as the thickness of the Yfe[SUB2] layers is increased. Two distinct ''instability fields'' can be identified: the bending field B[SUBB], signifying the onset of a magnetic exchange spring, and the irreversible switching field B[SUBIS] associated with magnetic reversal. We have developed a computational model to address this problem. In particular, it is shown that the two instability fields in question are characterized by vanishing eigenvalues in the matrix formed by the double energy derivatives λ[SUP2]E/λθ[SUBi]λθ[SUBj], where E is the total energy and θ[SUBi] the angle of each individual monolayer. It is shown that the model provides)a very good description of the M - B[SUBapp] loops of DyFe[SUB2]/Yfe[SUB2] multilayer films. In particular, the coercivity of a nearly magnetically compensated multilayer (75 ÅDyFe[SUB2]/150 ÅYfe[SUB2]) is much reduced below the prediction of the Stoner -- Wolhfarth model, in accord with experiment. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe[sub 2]/YFe[sub 2] superlattice samples with a (110) growth direction. In particular, the magnetic properties of the YFe[sub 2] dominated multilayer samples [wDyFe[sub 2]/4wYFe[sub 2]]xN with w=20, 30, 40, 45, 50, and 55 Å are presented and discussed. In principle, the multilayer films should possess similar magnetic properties because they are all nominally Dy[sub 0.2]Y[sub 0.8]Fe[sub 2]. However, it is shown that their magnetic properties depend strongly on the thickness of the DyFe[sub 2] layers w. Those films with w>=45 Å possess negative coercivities, while those with w≤40 Å are positive. It is argued that this behavior can be understood in terms of a strong increase of the intrinsic coercivity of the DyFe[sub 2]/YFe[sub 2] superlattice, taken as a whole, as w is reduced. For w≤40 Å almost none of the DyFe[sub 2] moments can be flipped over in the availa! ble field range (12 T). © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on room temperature ferromagnetic resonance (FMR) studies of [ t Co|2t Ni] × N sputtered films, where 0.1 ≤ t ≤ 0.6 nm. Two series of films were investigated: films with the same number of Co|Ni bilayer repeats (N = 12), and samples in which the overall magnetic layer thickness is kept constant at 3.6 nm (N = 1.2/t). The FMR measurements were conducted with a high frequency broadband coplanar waveguide up to 50 GHz using a flip-chip method. The resonance field and the full width at half maximum were measured as a function of frequency for the field in-plane and field normal to the plane, and as a function of angle to the plane for several frequencies. For both sets of films, we find evidence for the presence of first and second order anisotropy constants, K1 and K2. The anisotropy constants are strongly dependent on the thickness t, and to a lesser extent on the total thickness of the magnetic multilayer. The Landé g-factor increases with decreasing t and is practically independent of the multilayer thickness. The magnetic damping parameter α, estimated from the linear dependence of the linewidth ΔH, on frequency, in the field in-plane geometry, increases with decreasing t. This behaviour is attributed to an enhancement of spin-orbit interactions with decreasing Co layer thickness and in thinner films, to a spin-pumping contribution to the damping. [ABSTRACT FROM AUTHOR]

It has been known for many years that the rare-earth intermetallic compound terfenol (Tb[SUB0.3]Dy[SUB0.7])Fe[SUB2] is characterized by "giant magnetostriction," which has found practical applications. In this article we report the magnetic properties of a series of molecular beam epitaxially (MBE) grown (110) Tb[SUB1-x]Dy[SUBx]Fe[SUB2] alloy films, on sapphire substrates. All the measurements were performed at room temperature with the field applied along an in-plane [&1sline;10] axis. However, unlike bulk Tb[SUB1-x]Dy[SUBx]Fe[SUB2], it is shown that the coercivity does not fall to zero at the magic ratio of x ∼ 0.7. Instead, the coercivities fall almost on a straight line, with the maximum coercivity for pure TbFe[SUB2] (0.64 T) and the smallest for DyFe[SUB2] (0.22 T). The difference between the bulk and MBE films is attributed to the presence of a magnetoelastic strain term, induced during crystal growth by the sapphire substrate. In practice, the measured coercivities can be described, approximately, with a modified Stoner--Wohlfarth model. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe[sub 2]/YFe[sub 2] superlattice samples with a (110) growth direction. Detailed magnetization curves have been obtained for YFe[sub 2] dominated multilayer samples [wDyFe[sub 2]/4wYFe[sub 2]]x16 with w=45, 50, and 55 Å. In particular, it is shown that the formation of magnetic exchange springs in the magnetically soft YFe[sub 2] layers, can be used to engineer multilayer samples with a negative coercivity. Further, by using asymmetric field cycling procedures, we have investigated the irreversible parts of the M-B loop, associated with the switching of the DyFe[sub 2] multilayers. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxial methods have been used to grow single crystal Laves phase DyFe[sub 2]-YFe[sub 2] superlattice samples with a (110) growth direction. It is shown that it is possible, in principle, to engineer a desired coercivity between the limits K[sub DyFe[sub 2]]≤K≤∞. This can be achieved by adjusting the relative thickness of the individual DyFe[sub 2] and YFe[sub 2] layers, in multilayer films This novel feature is illustrated, using the superlattice films [x Å DyFe[sub 2]/(100-x) Å YFe[sub 2]]x40, with x=80, 60, 50, and 45. It is found that the measured coercivity is in semiquantitative agreement with a simple theoretical expression, for the nucleation fields in both bilayer and multilayer compounds. However, in practice, exchange spring penetration into the DyFe[sub 2] layers can set a limit to the maximum coercivity that can be achieved. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]