FMR Measurements Research Articles

FMR studies of Co 70(FeMo) 2Mn 5(BSi) 23 amorphous ribbons: Polishing effect

The part played by the surface imperfections on Co 70(FeMo) 2Mn 5(BSi) 23 amorphous ribbons due to the planar flow casting process has been pointed out by FMR measurements at 9 and 16 GHz and at 296 K and 77 K on as-quenced and field-annealed samples. From our curves and data we determine the role played by these macro- and micro- imperfections through the variations of the g-factor, the damping parameter λ, the transverse relaxation time T 2 as well as the maximum variations Δμ M , Δμ m and Δμ M of the relative magnetic permeability μ = μ - jμ.

Preparation of Metal Particle Catalysts Wrapped in Organosilicon Compound via Metal Vapor Synthesis

Three kinds of metal catalysts Ni/D 4 , Ni-Mn/D 4 , Ni-Mn-La/D 4 , wrapped in organosilicon compound were prepared by metal vapor synthesis. Their feature was characterized with XRD, TEM, XPS, FMR and static magnetic measurement. The metal particle size in catalysts was less than 3.5 am. The results of XPS showed that the metals in the catalysts existed in zero and other valent state. Inner metal, as an organosilicon compound folded around the metal particle, was protected from oxidation. FMR and static magnetic measuremeat revealed that metal particles were spheroidal and of superparamagnetism. Of all the caralysts the catalytic activity of Ni-Mn-La/D 4 was the highest in hydrogenating furfuraldehyde into furfuralcohol.

X-band FMR measurements: establishing of relations between the complex permeability and reflection factor of ferromagnetic amorphous conductors

A new calculation for the determination, at ultra-high frequencies, of the complex permeability variations of ferromagnetic amorphous conductors has been developed and gives the possibility of using directly the measurements obtained by ferromagnetic resonance. The equations set out and reported combine surface impedance relation, boundary conditions and variation studies of the magnetic field dependence of the reflection factor in the case of ultra-high frequencies. The measurements at 9 GHz have been led with an X-band three-wave interferometer of great accuracy with based-cobalt (Vitrovac) and based-iron-boron (Metglas) amorphous conductor samples

FMR measurements of Fe/MgO multilayers in submillimeter wave region

FMR measurements of Fe/MgO multilayers have been performed at 4.2 K in 220 and 370 GHz bands using pulsed magnetic field up to 15 T, which is well above the saturation field. The magnetic anisotropy and absorption intensity which depend on the thickness of the Fe layer have been obtained and discussed in connection with the magnetization measurements.

Amorphous (Co 93Zr 7) 100− xTb x thin films: magnetic properties and observation of new absorption modes

A study of the static and dynamic magnetic properties of amorphous (Co 93Zr 7) 100− x Tb x for small Tb substitution (0< x<3) is reported. As a result of the deposition conditions the perpendicular anisotropy is negligible but a small in-plane uniaxial anisotropy is formed, the magnitude of which increases with increasing RE content. The value of the coercive field is typical of a soft ferromagnet. The study of the dynamical properties — determined by FMR measurements — revealed that besides the Kittel resonance mode new type of absorption lines are detected. The evolution of these modes with film composition and experimental parameters are reported.

Perpendicular anisotropy in Co/Ru epitaxial superlattices

We present recent results on the magnetic properties of Co/Ru hcp superlattices. From magnetization and FMR measurements, we determine the rather strong uniaxial anisotropy, which tends to align the moments along the normal to the layers for Co thickness < 15 Å. This anisotropy is analyzed in terms of interface anisotropy and magneto-elastic anisotropy of the strained Co lattice which adds to the bulk magnetocrystalline anisotropy of the hcp oriented cobalt layers.

Magnetic properties and MOKE spectra of Fe/Pd CMF

Fe/Pd compositionally modulated films (CMF's) of various thicknesses prepared by vacuum evaporation were studied by VSM, FMR and MOKE spectra measurements. The room temperature magnetization of Fe layers and the polarization of Pd layers are deduced. At short wavelength the Kerr rotation of Fe/Pd CMFs increases with increasing polarization of the Pd layers. At long wavelengths the Kerr rotation, which is mainly contributed by the Fe layers, increases with Fe content.

Low temperature magnetic properties of calcium doped YIG

The FMR (K band) and magnetization measurements were performed on thin films of composition Y 3− x− y Ca x Pb y Fe 5O 12 , 0< x<0.39. The low temperature magnetization anomaly i.e. a decrease or a larger increase of the magnetization at T<50 K was observed which seems to depend on the lead content. The maxima in the temperature dependence of g eff and Δ H were attributed to a hopping mechanism associated with the O - ions.

FMR and EXAFS modeling of heat-treated Fe-rich and Co-rich TM-M thin films

Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedures, magnetic properties were calculated with no adjustable parameters. Correlation between perpendicular FMR measurements and EXAFS first-shell modeling suggests a low-temperature formation of cobalt-borides in the Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ alloy. Annealed Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ samples did not display evidence of structural and/or magnetic instabilities until the onset of long-range crystallization near T/sub ann/=400 degrees C.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ferromagnetic resonance in ultrathin Ni(111) /W(110)

20, 25 and 30 Å thin Ni(111) films have been prepared on W(110) in UHV and characterized by low energy electron diffraction and Auger spectroscopy. FMR measurements at 9 GHz have been used to study the magnetic properties between 300 and 600 K. The effective in and out of plane anisotropies increase with decreasing temperature and film thickness. These anisotropies are decomposed into surface ( K s) and volume ( K v) contributions. K v is 30 times larger than in bulk Ni, due to internal stress caused by the lattice mismatch between Ni and W.

Magnetic Properties of Sputtered Ni/Al Multilayers

AbstractMagnetic properties of sputtered Ni/Al multilayers have been investigated by vibrating sample magnetometry and ferromagnetic resonance. In these compositionally modulated films (CMFs) the Al ‘spacer’ layer thickness was fixed at 3.5 nm while the total Ni content of each film was held constant at 308 nm. The thickness of the individual Ni layers was varied from 4.8 to 154 nm. The CMFs showed a variety of magnetic characteristics which were dependent on the thickness of the Ni layers. CMFs with Ni layer thickness 30 nm and above showed clear evidence of perpendicular anisotropy. This anisotropy is characterized by low-remanence perpendicular hysteresis loops of the type commonly found in CoCr alloy films. As the Ni layer thickness diminishes the perpendicular anisotropy decreases and is eventually lost. Simultaneously, the CMFs show increasing in-plane remanence, rising to a peak squareness of greater than 0.5 at a Ni layer thickness of 11 nm. As the Ni thickness continues to decrease, the remanence again declines. At Ni thicknesses of a few nm the CMFs become quasi-superparamagnetic. These CMFs do not show a monotonic reduction in saturation magnetization, Ms, with decreasing Ni layer thickness. Instead, both Ms and the coercivity, Hc, pass through a maximum in the region of 40–80 nm Ni layer thickness. FMR measurements were also made on these films. A plot of the effective anisotropy field produces data of a similar form to the Ms versus Ni layer thickness plot, again with a clear maximum. The FMR data also reveals interesting resonances in the films exhibiting perpendicular anisotropy. The presence of satellite resonances adjacent to the principal resonance peaks seems to suggest, in structural terms, a two-phase system as the basis of the observed anisotropy.

FMR Measurements of Ion Implanted Amorphous FeCrSiB Ribbons

FMR Measurements of Ion Implanted Amorphous FeCrSiB Ribbons

Permeability and Anisotropy Dispersion of Amorphous Soft Magnetic Films

The frequency dependence of permeability has been calculated for soft magnetic thin films which have a uniaxial anisotropy with both amplitude and angular dispersion. These calculations have been performed for amorphous Co-Nb films, whose anisotropy dispersion has been determined by low-frequency FMR measurements. Comparison of the measured permeability with calculations suggests that the effective uniaxial anisotropy is dispersed more widely and with a smaller amplitude than is indicated by FMR measurements. The magnetization ripple is inferred to be one of the causes of the low value for the effective field.

Temperature dependent FMR on CoCr-layers

Temperature dependent FMR measurements were performed on two series of rf sputtered films. The FMR measuring temperature could be varied between 77 and 300 K. There is indication of the existence of 2 CoCr phases in the film from ion-milled samples. The perpendicular anisotropy increased with both decreasing temperature and stress-relaxation by removing the substrate.

Spin wave stiffness and the range of exchange interactions in amorphous (Fe1-xNix)75B25 and (Fe1-yWy)83B17 alloys

The variation of saturation magnetisation, Ms, with temperature has been derived from FMR measurements performed on amorphous (a-)(Fe1-xNix)75B25 and (Fe1-yWy)83B17 alloys in the temperature range 77 to 300 K. These data have been analysed to yield reliable values of the coefficients B, C of the T3/2, T5/2 terms in the spin wave expression for the fractional decrease in magnetisation with temperature and the mean-square range of the exchange interaction, (r2). The spin wave theory for amorphous ferromagnets due to Krey adequately describes the observed dependence of the above parameters (B, C, (r2)) on the Curie temperature, TC (determined from low-field (<or=10 Oe) bulk magnetisation data). The plot of spin wave stiffness coefficient, D, against TC for a-(Fe1-xNix)75B25 alloys is a straight line, well represented by the empirical equation D=D0+mTC, whose slope m exactly coincides with that predicted by the nearest-neighbour (nn) Heisenberg model and intercept, D0, on the ordinate gives the strength of the next-nearest-neighbour (nnn) exchange coupling constant which is at least one order of magnitude smaller than the nn exchange coupling constant. A plot of D against TC for a-(Fe1-yWy)83B17 alloys is again a straight line with the same slope m but passing through the origin (i.e. D0=0). This result is shown to imply that the competing interactions in W containing glasses confine the direct exchange to the nearest neighbours only whereas the exchange interactions in Ni containing alloys involve both the nearest as well as the next-nearest neighbours. Other important findings include (i) mixed exchange interactions cause more drastic reduction in the value of TC, Ms(0) and D than does simple magnetic dilution and (ii) for a given value of TC, D possesses a considerably lower value for the W substituted alloys than for the Ni substituted ones.

Spin wave resonance study of exchange-coupled Ni 80Fe 20 double layers separated by thin interlayers of Cu, Cr and Pd

We have performed ferromagnetic resonance measurements on thin polycrystalline Ni 80Fe 20 (permalloy) double layers with interlayers of Cu, Cr and Pd. Furthermore, a mathematical model is presented, which allows a calculation of resonance fields in the parallel configuration. Comparison of the calculated and measured resonance field values yields an interlayer exchange coupling constant A 12 as a function of interlayer thickness d. We observe exponential dependencies of A 12 on d for Cr, Cu and Pd interlayers with the strongest decay for Cr. Additionally, we present FMR measurements and calculations for a Ni 80Fe 20/Cr/Co heterostructure layer system.

軟磁性アモルファススパッタ膜の透磁率と異方性分散

Frequency dependence of permeability has been calculated for soft magnetic thin films which have amplitude and angular dispersion of the uniaxial anisotropy. The calculation has been adopted for amorphous Co-Nb films whose anisotropy dispersion has been determined by low frequency FMR measurements. Comparison of the measured permeability with the calculation suggests that the effective uniaxial anisotropy is dispersed more widely with low values than that obtained by the FMR method. The magnetization ripple is deduced to be one of the origins of the low effective field.

Effects of boron implantation in films of iron-nickel

We have implanted boron ions into films of Fe-Ni alloy composition. A homogeneous distribution of boron was determined from the sputter Auger analysis with a concentration of 18% and 34% for low- and high-dose implantation, respectively. The resistivity of film was increased by a factor of 2 and 4 as a result of low- and high-dose implantation, respectively. The magnetic properties of these films are studied as a function of annealing temperature by using FMR measurements. Both the uniaxial anisotropy field and FMR linewidth are dramatically decreased as a result of annealing at elevated temperatures. The changes of effective magnetization of these films are strongly dependent on implanted boron concentration.

Torque anisotropy and magnetization in Mo/Ni superlattices

Angular and field varying torque measurements have been made on Mo/Ni superlattices. The angular results show good agreement with FMR measurements, indicating no frequency-dependent aspects of the anisotropy at room temperature. It is observed that field varying measurements provide an accurate, inexpensive method of determining the magnetization, but the magnetic anisotropy obtained by this technique differs significantly from FMR and angular results.

Spin-wave resonance in single-crystal epitaxial iron films (abstract)

We have made ferromagnetic resonance measurements on single-crystal films of iron on ZnSe/GaAs substrates using field and frequency swept techniques. For field swept measurements the magnetic field was applied normal to the film plane and the frequency was fixed at 9.50 Hz. We find that spin-wave resonance (SWR) modes are excited in addition to a localized surface mode.1 The SWR modes obey an n2 law, where n is the spin-wave order number and a value of A/M=1.28×10−9 Oe cm2 (where A is the exchange stiffness constant and M the magnetization) is deduced from the data. This value is in reasonable agreement with that obtained1 on iron films grown directly on GaAs substrate. The fact that higher-order spin-wave mode linewidths increase only slightly from the main line linewidth of 30 Oe implies that these films are of improved quality in comparison to previous films. For the frequency swept measurements2 the frequency was swept from 0.01 to 20 GHz continuously. Ferromagnetic resonance was measured in zero field at 14.8 GHz. The measured resonance frequency compares reasonably well with the calculated value of 14.2 GHz using only measured3 static field values of 4πM=20.9 kG, g=2.10, 2k1/M=560 Oe, and 2ku/M =460 Oe. The inclusion of ZnSe epilayer in between the iron film and GaAs substrate have improved the quality of the iron film as manifested in our FMR measurements. The linewidth of each spin-wave and main mode excitations are the narrowest values measured to date in iron films.