Angular Dependence Of Resonance Field Research Articles

Effects of second order surface anisotropy in YIG sputtered onto GGG (1 0 0) oriented substrate

In this work, we produced Y3Fe5O12 textured films, with thicknesses between 50 nm and 500 nm, onto (1 0 0) Gd3Ga5O12 by magnetron sputtering and post annealing, and investigated the first and second order surface and cubic anisotropy constants using the ferromagnetic resonance technique. The surface anisotropy constants exhibited different behaviors with film thickness, with the first order presenting the usual inverse of ferromagnetic layer thickness. Besides this inverse of thickness behavior, the second order also came up with a constant value. In the frame of spin reorientation transition phenomenon, we evaluated volume and surface contribution to the surface anisotropy. Although the second order cubic anisotropy constant is one order of magnitude stronger than the first order, they did not show any explicit thickness dependence. The second order terms of surface and cubic anisotropy appeared to be essential to allow simultaneous fit of in-plane and out-of-plane angular dependence of resonance field. Moreover, they had to be negative to describe the out-of-plane results correctly. Our results raised critical issues that shall be taken into account when explaining the new and recent spintronics and caloritronics effects in YIG.

Ferromagnetic resonance investigation in permalloy magnetic antidot arrays on alumina nanoporous membranes

The magnetic properties of Ni80Fe20 antidot arrays with hole diameters of 18 and 70nm fabricated by a template-assisted method were investigated using the ferromagnetic resonance technique. Tuning the antidot arrays by changing the hole diameter enables control on the angular dependence of the ferromagnetic resonance field. The scanning electron microscope images reveal a quite regular hexagonal arrangement of the pores, however the angular dependence of the resonance field do not exhibit the six-fold symmetry expected for this symmetry. Micromagnetic simulations performed on a perfect hexagonal lattice, when compared with those made on our real system taken from the scanning microscope images, reveal that the presence of defects in the antidot lattice affects the ferromagnetic resonance field symmetry.

Antiferromagnetic layer thickness dependence of noncollinear uniaxial and unidirectional anisotropies in NiFe/FeMn/CoFe trilayers

We have investigated the dependence of magnetic anisotropies of the exchange-biased NiFe/FeMn/CoFe trilayers on the antiferromagnetic (AF) layer thickness $({t}_{\text{AF}})$ by measuring in-plane angular-dependent ferromagnetic resonance fields. The resonance fields of NiFe and CoFe sublayers are shifted to lower and higher values compared to those of single unbiased ferromagnetic (F) layers, respectively, due to the interfacial exchange coupling when ${t}_{\text{AF}}\ensuremath{\ge}2\text{ }\text{nm}$. In-plane angular dependence of resonance field reveals that uniaxial and unidirectional anisotropies coexist in the film plane, however, they are not collinear with each other. It is found that these peculiar noncollinear anisotropies significantly depend on ${t}_{\text{AF}}$. The angle of misalignment displays a maximum around ${t}_{\text{AF}}=5\text{ }\text{nm}$ and converges to zero when ${t}_{\text{AF}}$ is thicker than 10 nm. Contributions from thickness-dependent AF anisotropy and spin frustrations at both F/AF interfaces due to the structural imperfections should be accounted in order to understand the AF-layer thickness dependence of noncollinear magnetic anisotropies.

Effect of temperature on the magnetic properties of Fe3O4 thin films studied by ferromagnetic resonance (FMR)

AbstractSingle crystalline Fe3O4 thin films of 110 Å thickness grown on MgO (100) substrate have been investigated by Ferromagnetic Resonance (FMR) technique as a function of temperature between 3 and 300 K. A strong unidirectional (exchange) anisotropy field was detected as evidence from a shift of the resonance field for the r‐FC case relative to that for n‐FC case at lower temperature. Using a field‐induced unidirectional exchange and bulk anisotropy, with the usual magneto‐crystalline cubic anisotropy energy, we have simulated both the experimental spectra and angular dependence of resonance field to deduce anisotropy and other magnetic parameters as a function of temperature. Magnetic parameters and Verwey transition for the thin film case were found to shift down to around 90 K from 120 K for bulk sample of the same compound as well. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Magnetic anisotropy in GaP(001) epilayers containing MnP nanoclusters observed by angle dependent ferromagnetic resonance measurements

We report on the angular dependence of ferromagnetic resonance (FMR) of GaP(001) epilayers with embedded MnP nanoclusters (GaP:MnP) grown on a GaP(001) substrate using metal-organic vapor phase epitaxy (MOVPE). Angle dependent FMR spectra obtained at 292K show several peaks and indicate a strong magnetic anisotropy. The measured angular dependence of resonance fields can be modeled assuming that the MnP clusters possess a strong biaxial magnetocrystalline anisotropy whose axes are oriented along specific GaP crystallographic directions. Dominant populations of MnP clusters have their b-axis along GaP [111] and [111¯] directions, while a smaller population has the b-axis along the GaP [001] direction. In comparison, angle dependent FMR spectra of a polycrystalline MnP thin film grown on a GaP(001) substrate using MOVPE suggest that the crystals b-axis is oriented favorably along the GaP [001] direction.

Influence of spacer layer in exchange coupled NiFe/Cu/IrMn trilayer structure

Variations in exchange coupling for NiFe/Cu/IrMn trilayer thin films were examined as a function of the Cu spacer thickness. The exchange coupling field and an uniaxial anisotropy field were analyzed by ferromagnetic resonance measurements with an angular variation. Angular dependence of resonance field showed unidirectional behavior but the film with thick Cu layer showed a similar trend to uncoupled NiFe single layer film. As Cu spacer thickness increase, the exchange coupling field and the uniaxial anisotropy field decreased with different decrease trend from Cu spacer thickness of 0.8 nm.

The study of exchange coupling in NiFe/Cu/IrMn trilayer structures by MOKE and FMR measurements

The exchange coupling strength of NiFe/Cu/IrMn trilayer films was examined with both a new magneto optical Kerr effect (MOKE) method developed for the exchange coupling field determination and ferromagnetic resonance (FMR) measurements. We found that the value for exchange coupling field obtained by the MOKE technique coincided with FMR result with high accuracy. Other peculiarities of FMR measurements due to interlayer exchange coupling such as angular dependence of resonance field on Cu spacer thickness are also shown in the article.

Combined Ferromagnetic Resonance and Magnetic Force Microscopy Studies in Arrays of Magnetic Nanowires

Present study reports on magnetostatic interactions in highly-ordered arrays of Ni nanowires embedded in nanoporous alumina membranes. We use two techniques supplying complementary information: ferromagnetic resonance, FMR, studies from which we derive information of the whole array of nanowires, and magnetic force microscopy, MFM, that informs us about the magnetic state of individual nanowires. From FMR study of the angular dependence of resonance field and itsline-width it is concluded that the magnetostatic interaction plays an important role to decrease the effective anisotropy field of individual nanowires. This is confirmed by analysis of MFM images at remanence and its comparison with vibrating sample magnetometer measurements.

High-Spin Nitrenes with s-Triazine Skeleton

Heteroatomic high-spin molecules are suitable for a model study of room-temperature stable molecular based magnetics. We studied high-spin nitrenes (S = 1 and 2) with s-triazine skeleton, which were generated by the photolysis of the polyazide precursor. We identified mononitrene 1 (S = 1) and bisnitrene 2 (S = 2) for the first time by single-crystal ESR measurements. The fine-structure parameters were determined by the angular dependence of resonance fields. The determined fine-structure parameters were |D| = 1.402 cm−1 and |D| = 0.280 cm−1 for mononitrene 1 and bisnitrene 2, respectively. The large D values indicate that π-spin delocalization effects were hampered by introducing heteroatoms to π-spin systems. The hyperfine splittings due to the monovalent nitrogen nucleus of 1 were observed with magnetic field along the principal axis of the fine structure tensor. The hyperfine splitting constant was about 0.0018 cm−1. The temperature dependence of ESR signals showed that 1 and 2 were triplet and quintet in the ground state, respectively.

Effect of cubic magnetic anisotropy on angular dependences of the resonance field in (111)-oriented films

The angular dependences of the ferromagnetic resonance (FMR) field in (111)-oriented films are analyzed with the use of resonance relations and the conditions for equilibrium orientation of the magnetization. Based on the results obtained, an FMR method is proposed for determining the sign of the cubic anisotropy and the position of the crystallographic axes.

FMR study on some magnetic granular films

We have measured the angular dependence of the ferromagnetic resonance (FMR) spectra for two systems of magnetic granular films: Ag-Co and Ni-SiO/sub 2/. In these two systems, the concentration of the magnetic component was varied to tune the magnetic properties, which were reflected from the FMR spectra. Our results have shown that the angular dependences of resonance field and the line width of these samples are changed significantly with the concentration of magnetic component.

Angular dependence of the main resonance field in the spin wave spectra of single-crystal nickel films

Measurements of the position of the main resonance in the spin wave spectra of single-crystal nickel films at 17 GHz have been performed, at room temperature, as a function of angle between the applied magnetic field and the film normal. The analysis shows that the general behaviour of the angular dependence of the resonance field is due to the angular variation in the demagnetizing field. Additional information concerning the general character of the resonance field measured at oblique angles is also discussed. Theoretical curves obtained from calculations of the resonance field are in good agreement with the experimental observations.

Effect of annealing in vacuum on the magnetic anisotropy of Ag-doped CdCr 2Se 4 crystals

Angular dependences of resonance field and linewidth have been measured for ferromagnetic CdCr 2Se 4 crystal doped with 1.5 mol.% Ag before and after annealing in vacuum. The change of the sign of anisotropy due to annealing is associated with transformations Cr 4+→Cr 3+→Cr 2+. On the basis of obtained data some suppositions are made about the mechanisms of conductivity in the Ag-doped CdCr 2Se 4 crystal.

Antiferromagnetic Resonance of Europium Telluride

Antiferromagnetic resonances for the bulk and thin film samples of europium telluride single crystal have been performed at the frequencies of 9.20 and 33.99 GHz. Angular dependences of resonance field in the cases of external field applied in and out-of the (111) plane are investigated. The easy and hard directions of the small anisotropy in the (111) plane are determined as and , respectively. Frequency diagram is obtained in symmetrical by scaling the modified field (1+κ 2 ) 1/2 · H 0 as an abscissa. Temperature dependences of resonance field are measured in temperatures above and below the Neel temperature, and the temperature dependence of anisotropy energy constants in the (111) plane is obtained. Its noticeable result is that the anisotropy energy constants in the (111) plane decrease with the decreasing temperature.