In-plane Uniaxial Anisotropy Field Research Articles

Ultrahigh in-plane uniaxial magnetic anisotropy of amorphous FeCoHf composition gradient films

Amorphous FeCoHf films with a Hf composition gradient were prepared at room temperature. The composition gradient sputtering technique was used to control the composition gradient of the doped element Hf by changing the deposition power of Hf. Interestingly, in the as-deposited FeCoHf films, an in-plane uniaxial magnetic anisotropy field of up to 640 Oe was achieved, and the resonance frequency was 6.5 GHz. The large anisotropy field can be attributed to the high sensitivity of the amorphous FeCoHf films to the composition gradient. The ultrahigh anisotropy exhibited by FeCoHf films at room temperature holds significant technological potential for various applications.

Effect of external stress anisotropy on the ferromagnetic resonance properties in thin film

Effects of in-plane and out-of-plane external stress anisotropy of ferromagnetic thin film with in-plane and out-of-plane uniaxial anisotropy on the ferromagnetic resonance frequencies have been theoretically investigated by using ferromagnetic resonance method. It is shown that resonance frequency can be enhanced by increasing in-plane external stress anisotropy field and uniaxial anisotropy field, decreasing out-of-plane uniaxial anisotropy field. For out-of-plane external stress case, however, the resonance frequency and two critical fields have no significant change. Also, compared with the case of the in-plane external stress anisotropy, the FMR frequencies are smaller. Additionally, interesting features are obtained for the stress case and compared with the case of without stress. The obtained results provide further insights on the effect of external stress on the properties of ferromagnetic thin film.

Twofold and fourfold anisotropies in zinc ferrite thin films investigated by ferromagnetic resonance

By means of the ferromagnetic resonance (FMR) technique (at the $X$ band) we investigated the magnetic properties of ${\mathrm{ZnFe}}_{2}{\mathrm{O}}_{4}$ (ZFO) films grown on different substrates. Angular dependence of the FMR field showed the existence of twofold and fourfold anisotropies for the same material, grown on Si(111), MgO(100), and STO(100), respectively. By using a model that takes into consideration the relevant contributions to the energy, we were able to extract the following parameters: effective magnetization ${M}_{\mathrm{eff}}$, cubic magnetocrystalline anisotropy field, in-plane and out of plane uniaxial anisotropy fields, and the $g$ factor. The samples deposited on Si showed a twofold in-plane anisotropy while a fourfold magnetic anisotropy was observed for the ZFO/MgO and ZFO/${\mathrm{SrTiO}}_{3}$ samples. All samples showed a strong perpendicular uniaxial anisotropy above 1 kOe and low in-plane uniaxial and cubic anisotropy field, on the order of tens of oersteds. The FMR linewidth ($\mathrm{\ensuremath{\Delta}}H$) fitted from FMR data shows $\mathrm{\ensuremath{\Delta}}H$ values above 190 Oe for all samples, indicating high damping of this material to be $\ensuremath{\sim}{10}^{\ensuremath{-}2}$ for the ZFO/MgO. The present analysis compared the FMR data obtained for the in-plane and out of plane measurements. Likewise, the effective magnetization and perpendicular uniaxial anisotropy field by FMR were compared with the magnetic response obtained by a vibrating sample magnetometer.

Theoretical investigation of ferromagnetic resonance in a ferromagnetic thin film with external stress anisotropy

We use the ferromagnetic resonance (FMR) method to study the properties of ferromagnetic thin film, in which external stress anisotropy, fourfold anisotropy and uniaxial anisotropy are considered. The analytical expressions of FMR frequency, linewidth and the imaginary part of magnetic susceptibility are obtained. Our results reveal that the FMR frequency and the imaginary part of magnetic susceptibility are distinctly enhanced, and the frequency linewidth or field linewidth are broadened due to a strong external stress anisotropy field. The hard-axis and easy-axis components of magnetization can be tuned significantly by controlling the intensity and direction of stress and the in-plane uniaxial anisotropy field.

Large anisotropy of magnetic damping in ultrathin epitaxial Fe/GaAs (0 0 1) film

The magnetization dynamics of ultrathin epitaxial Fe films on GaAs (0 0 1) with different thicknesses have been investigated by all-optical time-resolved magneto-optical Kerr effect. For the Fe film with thickness of 8 monolayers, the magnetic damping constant along orientation increases by 66% compared with that along orientation, showing the uniaxial anisotropy of magnetic damping. By the measurement of angular dependent time-resolved magneto-optical Kerr effect, the uniaxial magnetic damping is clearly correlated to the in-plane uniaxial anisotropy field of the Fe film. In addition, the anisotropy of the damping constants is found to disappear for the Fe films thicker than 15 monolayers, suggesting that the anisotropic damping originates from the interfacial effect between Fe and GaAs.

Fabrication and ferromagnetic resonance study of BZT-BCT/LSMO heterostructure films on LAO and Pt

Abstract In this article, dynamic magnetic properties of La0.7Sr0.3MnO3 (LSMO) thin film capped with a Pb-free ferroelectric BZT-BCT layer deposited on two different substrates, i.e. lanthanum aluminate (LAO) and Platinum (Pt), by pulsed laser deposition (PLD) have been investigated using ferromagnetic resonance (FMR) spectroscopy. The heterostructures of BZT-BCT/LSMO on LAO substrate were highly (0 0 l)-oriented whereas these were randomly oriented on Pt substrate. The well-behaved M-H hysteresis loops were observed at room temperature for both heterostructures indicating the ferromagnetic behavior of LSMO. The right shift of the hysteresis loop of the heterostructure was observed due to the magnetoelectric coupling between ferroelectric and ferromagnetic layers. The FMR measurements yield optimum values of different important parameters such as the linewidth offset, Gilbert damping, gyromagnetic ratio, and in-plane uniaxial anisotropy field of the thin films, which are essential to design spin valve and magnetic tunneling based devices. We found the lowest Gilbert damping parameter of ∼0.03 for the BZT-BCT/LSMO/LAO heterostructure due to spin orbit coupling. In addition, the gyromagnetic ratio was also obtained to be small (0.002 GHz/Oe) in the same film. These results open new possibilities to use BZT-BCT/LSMO heterostructure for future spintronic device applications.

Influence of Deposition Cycle and Magnetic Annealing on High-Frequency Magnetic Properties of the [Co90Fe10/Ta]<italic>n</italic> Multilayer Thin Films

In this paper, a series of [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /Ta] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> multilayer thin films with various deposition cycles n were prepared by magnetron sputtering. The crystal structure, top-surface topography, and static and dynamic magnetic properties of [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /Ta] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> multilayer thin films were investigated systematically. The results showed that the deposition cycle n has slight impact on the high-frequency magnetic performance of the multilayer thin films except damping coefficient α and real part of permeability μ'. Moreover, we studied the influence of magnetic annealing temperature (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> ) on high-frequency soft magnetic properties of [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /Ta] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> multilayer thin films. It was found that saturation magnetization, coercivity, in-plane uniaxial magnetic anisotropy field, damping coefficient, and real part of permeability were all highly dependent on T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> . When T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> = 250 °C, the [Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">90</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> /Ta] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> multilayer thin film exhibited a relatively good comprehensive performance: saturation magnetization 4πM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> = 13.06 kG, in-plane uniaxial magnetic anisotropy fields H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</sub> = 42 Oe, easy-axis coercivity H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ce</sub> = 2.8 Oe, ferromagnetic resonance frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.25 GHz, and real permeability μ' = 255.

Electric-regulated enhanced in-plane uniaxial anisotropy in FeGa/PMN–PT composite using oblique pulsed laser deposition

The FeGa film with in-plane uniaxial magnetic anisotropy was fabricated onto different oriented single-crystal lead magnesium niobate–lead titanate using oblique pulsed laser deposition. An enhanced in-plane uniaxial magnetic anisotropy field of FeGa film can be adjusted from 18 Oe to 275 Oe by tuning the oblique angle and polarizing voltage. The competitive relationship of shape anisotropy and strain anisotropy has been discussed, which was induced by oblique angle and polarizing voltage, respectively. The (100)-oriented and (110)-oriented PMN–PT show completely different characters on voltage-dependent magnetic properties, which could be attributed to various anisotropy directions depended on different strain directions.

The evolution of in-plane magnetic anisotropy in CoFeB/GaAs(001) films annealed at different temperatures

A considerable in-plane uniaxial magnetic anisotropy (UMA) field (Hu ∼ 300 Oe) could be achieved when the amorphous CoFeB film was deposited on the GaAs(001) wafer by magnetron-sputtering after proper etch-annealed procedure. In order to get deep insights into the mechanism of the UMA, the film was annealed at different temperatures and the evolution of the in-plane magnetic anisotropy was investigated carefully. With increasing the annealing temperature (TA), the UMA could be maintained well when TA reached 250°C, but became very weak at 300°C. However, when TA was elevated to 400°C, another UMA (Hu ∼ 130 Oe) was built accompanied with a fourfold magnetic anisotropy with its strength of about 50 Oe. In terms of the magnetic anisotropy evolution along with TA, the anelastic strain, which is thought to be resulted from the interfacial interaction between CoFeB and GaAs, may play a dominant role in producing the enhanced UMA based on the ‘bond-orientational’ anisotropy (BOA) model.

Gilbert damping in CoFeB/GaAs(001) film with enhanced in-plane uniaxial magnetic anisotropy

A 3.5 nm amorphous CoFeB film was sputtered on GaAs (001) wafer substrate without applying magnetic field during deposition, and a significant in-plane uniaxial magnetic anisotropy (UMA) field (Hu) of about 300 Oe could be achieved. To precisely determine the intrinsic Gilbert damping constant (α) of this film, both ferromagnetic resonance (FMR) and time-resolved magneto-optical Kerr effect (TRMOKE) techniques were utilized. With good fitting of the dynamic spectra of FMR and TRMOKE, α is calculated to be 0.010 and 0.013, respectively. Obviously, the latter is 30% larger than the former, which is due to the transient heating effect during the TRMOKE measurement. In comparison with ordinary amorphous CoFeB films with negligible magnetic anisotropies, α is enhanced significantly in the CoFeB/GaAs(001) film, which may be mainly resulted from the enhanced spin-orbit coupling induced by the CoFeB/GaAs interface. However, the significant in-plane UMA plays minor role in the enhancement of α.

Modulation of magnetic damping constant of Fe2Co films by heavy doping of rare-earth Yb

The effect of rare-earth element Yb doping on modulating the magnetic properties, especially the damping constant, is investigated in a series of amorphous (Fe2Co)(1−x)Ybx thin films by the time-resolved magneto-optical Kerr effect at room temperature. A linear decrease of the saturation magnetization and in-plane uniaxial anisotropy field with the increase of x was observed and explained by the diluted effect of non-magnetic Yb doping. The magnetic damping constant performs a remarkable increase with Yb concentration. X-ray photoelectron spectroscopy reveals partial oxidation of Yb, which has large orbital moment and the associated large spin–orbital coupling (SOC) strength and may be responsible for the increased damping constant in contrast with the expected weak SOC and associated low damping constant of metallic Yb doping.

Double permeability peaks in Ce9Fe91films with in-plane uniaxial anisotropy

Ce9Fe91films were fabricated at different temperature by Rf magnetron sputtering. The static and dynamic magnetic properties of these films have been investigated in details. The results reveal that the two films prepared at 293K and 623K with the critical film thickness exhibit weak stripe domains and a small perpendicular anisotropy, and their correlated dynamic permeability spectra show one resonance peak, implying the coherent precession of magnetization at such critical thickness. However, the film prepared at 523K possesses an in-plane uniaxial anisotropy and lower coercive field. And the permeability spectrum displays two peaks, which can be ascribed to the coexistence of the rotatable anisotropy and in-plane uniaxial anisotropy.

Dynamic magnetic characteristics of obliquely sputtered Co2FeSi film with ultrahigh in-plane uniaxial anisotropy

We performed systematically studies on the magnetostatic and magnetodynamic properties of obliquely deposited Co2FeSi thin films. By varying the oblique deposition angle of Co2FeSi films, we induced a large in-plane uniaxial magnetic anisotropy field with the maximum value of 626.7 Oe at oblique angle of 39°, which significantly enhanced its zero-field ferromagnetic resonance (FMR) frequency up to 10.8 GHz. The magnetodynamic parameters such as Gilbert damping factor and exchange stiffness of Co2FeSi films were determined from the uniform FMR mode and the first perpendicular standing spin-wave, respectively. It is found that the Gilbert damping factor can be easily tuned from 0.006 to 0.013 by changing oblique deposition angle, whereas the exchange stiffness stays almost constant. These Co2FeSi films with tunable magnetic properties might be a good candidate for applications in both conventional and spintronics microwave devices.

Magnetic properties of [FeCoSiN/SiNx]18 multilayer thin films for applications in GHz range

[FeCoSiN/SiNx]18 multilayer thin films with different SiNx layer thickness (t) ranging from 0.75 to 4 nm were fabricated by reactive magnetron co-sputtering without applying an external induced magnetic field. The grain size, morphology, electrical properties, and static and dynamic magnetic properties of [FeCoSiN/SiNx]18 multilayer thin films were investigated systematically. The results indicated that SiNx layer thickness had a profound impact on the physical properties of the multilayer thin films. The in-plane uniaxial magnetic anisotropy field (from 114 ± 21 to 163 ± 14 Oe), ferromagnetic resonance frequency (from 4.09 to 4.64 GHz) and resistivity (from 188 to 333 μΩ cm) could be tailored effectively by adjusting the SiNx layer thickness from 0.75 to 4 nm. Moreover, when the SiNx layer thickness reached 2 nm, the continuous growth of FeCoSiN polycrystalline layers was to be interrupted completely and it would result in a minimum grain size of 4.9 ± 0.7 nm. The root mean square roughness of multilayer thin films also acquired a minimum value of 0.8 nm and the corresponding easy axis coercivity achieved a minimum value of 2.8 ± 0.1 Oe.

Adjustable high-frequency magnetic properties of oriented Co80Ir20 soft magnetic thin films with strong negative magnetocrystalline anisotropy

The oriented Co80Ir20 soft magnetic thin films with adjustable in-plane uniaxial anisotropy field and strong negative magnetocrystalline anisotropy ( $$K_{\text{u}}^{\text{grain}}$$ ) were fabricated by magnetron sputtering. The oblique angle dependence of the static and high-frequency properties for the oriented Co80Ir20 soft magnetic films was systematically investigated. The results suggest that the in-plane uniaxial anisotropy field (H u) can be adjusted by changing the oblique angle, while the total out-of-plane anisotropy field remains invariable. With the increase in the oblique angle, the value of H u varies from 80 to 310 Oe. As a result, the natural resonance frequency (f r) significantly increases from 4.6 to 7.9 GHz.

Electric field induced natural resonance and magnetic damping in FeCo/ Pb (Mg1/3Nb2/3) O3-PbTiO3 heterostructures

We demonstrated that magnetic damping and natural resonance frequency could be modulated by the electric field in an FeCo layer on Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) heterostructures by the microstrip method with a vector network analyzer. Strain mediated natural resonance increased from 0.8 to 2 GHz with increasing the electric field from 0 to 12.5 kV cm−1. Furthermore, the magnetic damping factor increased from 0.008 to 0.225, which resulted from magnetization precession under a microwave field and interface charge mediated spin current due to the spin screening effect. The results were also validated by the measurements of ferromagnetic resonance, which was also clear from analysis of the intrinsic and extrinsic contributions to the magnetic damping. In addition, in-plane uniaxial static magnetic anisotropy field was also modulated from 8 to 200 Oe with a different electric field.

High-frequency properties of oriented hcp-Co1−xIrx (0.06 ≤ x ≤ 0.24) soft magnetic films

In this work, the composition dependence of high-frequency magnetic properties for the oriented hcp-Co1−xIrx soft magnetic films with negative uniaxial magnetocrystalline anisotropy (Kugrain) and in-plane uniaxial anisotropy field (Hu) is investigated. Both the saturation magnetization (Ms), Kugrain, and Hu are greatly affected by the composition of Ir. The (μi−1)⋅fr of Co1−xIrx (with negative Kugrain) is larger than Acher's limit (without Kugrain) when x exceeds 0.14. The increasing percent of (μi−1)⋅fr could get a maximum of 42% when x is 0.2.

Controlling the microwave characteristic of FeCoB-ZnO granular thin films deposited by obliquely sputtering

A series of FeCoB-ZnO soft magnetic granular films deposited at different oblique angles were prepared by magnetron sputtering system. A variable in-plane uniaxial magnetic anisotropy field from 27.6 Oe to 212 Oe and an adjustable ferromagnetic resonance frequency from 1.89 GHz to 5.3 GHz were obtained in the as-deposited films just by increasing the oblique angle from 15° to 56°. Frequency line-width and effective Gilbert damping factor were both insensitive to the different oblique angles (αeff decreased from 0.036 to 0.03 and Δf decreased from 1.49 to 1.27), which almost satisfied the requirement that fFMR could be tuned independently in a certain frequency range. Besides, the change of dynamic magnetic anisotropy field versus oblique angle was illustrated and analyzed quantitatively compared with the static magnetic anisotropy.

Electromagnetic and microwave properties of NiFe/NiFeO multilayer thin films

In this work, [NiFe/NiFeO]10 multilayer thin films were fabricated by magnetron sputtering. The microwave and electromagnetic properties were investigated for different thicknesses, t, of the NiFeO layer (t = 0–6 nm) while the thickness of the NiFe was maintained at 8 nm in every cycle. A clear in-plane uniaxial anisotropy field was induced by an external magnetic field. The in-plane uniaxial anisotropy can be adjusted by tailoring the thickness of the NiFeO layer. When t = 0 nm, the NiFe monolayer, which has a thickness of 80 nm, showed low resistivity (ρ) and ferromagnetic resonance frequency (f r ). By increasing the t from 0 to 6 nm, the ρ of the [NiFe/NiFeO]10 films exhibited a significant monotonic increase (from 111.2 to 268.8 μΩ cm), the f r rose from 1.07 to 2.85 GHz, and the saturation magnetization (4πM s ) was decreased from 12.7 to 10.8 kG. The real part (μ′) of the complex permeability is larger than 100 in the range 0.2–1.9 GHz and the damping coefficient (α eff ) increases to 0.078 for t = 6 nm.

Improved high-frequency soft magnetic properties of FeCo films on organic ferroelectric PVDF substrate

Abstract FeCo films with various thicknesses were fabricated by direct-current magnetron sputtering on corning glass and organic ferroelectric PVDF substrates at the same time with 5 nm Ru seed layer and 5 nm Ta protective layer. The in-plane uniaxial anisotropy field of FeCo on glass substrate increases from 24 to 36 Oe with the increase of FeCo film thickness from 5 to 100 nm. However, a large in-plane anisotropy field of FeCo on PVDF substrate increases with FeCo thickness from 5 to 20 nm and gradually decreases with the FeCo thickness further increasing. Atomic force microscope images of FeCo on glass show quite smooth surface with root-mean-square roughness around 0.5 nm and have none visible granules on the surface for all samples. While, AFM images of FeCo on PVDF show quite rough surface with RMS roughness around 25 nm and have visible granules with the smallest granules appearing at the FeCo thickness of 20 nm. The permeability spectra show the typical ferromagnetic resonance phenomenon and can be well fitted by the LLG equation with the obtained experimental parameters. The ferromagnetic resonance frequency can reach 7.0 GHz for the 20 nm FeCo film on PVDF. Moreover, the quality factor of this sample can respectively reach 26, 12 and 7 at 1.0, 2.0, and 3.0 GHz, indicating the potential real 3G application for high-frequency devices.