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In the present work, we have modeled a heterogeneous Magneto Resistance Tilted Polarizer-based Spin Torque Nano Oscillator [MRTP-STNO] theoretically. The idea of the work is to investigate the impact of thermal noise on the frequency as well the PSD of the above mentioned device by including the Hth in the Heff. The precession of magnetization dynamics led by Spin Transfer Torque [STT] is studied numerically by solving the equation called Landau-Lifshitz-Gilbert-Slonczewski [LLGS]. Here, β is the independent tilt angle of the fixed layer and θ is the angle between free layer magnetization and the easy axis of the device, respectively. Both the angles can be varied from 10° to 90° as an increment of 10°. The maximum frequency of the modeled device is about 235.5 GHz and PSD of 1.74 µW/mA2/GHz in the absence of thermal noise and in the presence of thermal noise the frequency as well as the corresponding PSD is recorded as 215.4 GHz and PSD of 1.70 µW/mA2/GHz. The author sparks that the modeled device applies to High-Frequency applications and opens a new platform for forthcoming devices during its practical usage. [ABSTRACT FROM AUTHOR]

In this study, we have modeled a simple Spin Torque Nano Oscillator [STNO] of Tri and Penta layer structure theoretically, using macro-spin approach. Tri-layer Spin Torque Nano Oscillator [T-STNO], refers to a device made up of three layers comprising of a couple of Ferro-Magnetic layers separated between a Non-Magnetic [NM] spacer (i.e.) [FM1/NM1/FM2]. Penta-layer Spin Torque Nano Oscillator [P-STNO] refers that the device is made up of five layers which comprised of three FM layers aligned between two NM spacer (i.e.) [FM1/NM1/FM2/NM2/FM3]. The idea of the work is to investigate and report the results of the P-STNO, (which grabbed many researchers' attention) and to compare its functionalities with the conventional T-STNO which has been commercialized, already. The magnetization precession dynamics led by Spin Transfer Torque [STT] is studied numerically by solving the equation called Landau-Lifshitz-Gilbert-Slonczewski [LLGS]. The author wishes that the designed P-STNO device open a new window for the spintronic based devices because of its superior output functionalities as compared to the conventional T-STNO device. [ABSTRACT FROM AUTHOR]

Here, tShe authors have designed a heterogeneous Current Induced Oersted Field based Magneto Resistance Tilted Polarizer-Spin Torque Nano Oscillator [CIOF-MRTP-STNO] in a theoretical manner. The idea of the work is to investigate the impact of thermal noise on the frequency as well the PSD of the above modelled device by including the Hth in the Heff by macro-magnetic approach. The magnetization precession dynamics guided by Spin Transfer Torque [STT] is studied numerically by solving the governing equation called Landau-Lifshitz-Gilbert-Slonczewski [LLGS]. Here, β is the independent tilt angle of the fixed layer and θ is the angle between free layer magnetization and the easy axis of the device, respectively. In the device, both the angles β and θ can be varied from 10° to 90° as an accretion of 10°. The maximum frequency of the modeled device is about 197 GHz and PSD of 1.67 µW/mA2/GHz in the presence of thermal noise with Hoe = 50 kA/m (in the presence of CIOF), but in the absence of thermal noise, the frequency and the PSD emitted by the device is reduced to 180 GHz and 1.63 µW/mA2/GHz. On the other hand, in the presence of thermal noise with Hoe=0 kA/m (in the absence of CIOF), the device emits the frequency and PSD of 137 GHz and 1.51 µW/mA2/GHz, but in the absence of thermal noise, the frequency and the PSD emitted by the device is reduced to 125 GHz and 1.48 µW/mA2/GHz. The author suggests that the modeled device is applicable to High-Frequency applications. [ABSTRACT FROM AUTHOR]

Spin wave propagation in air-gap stripes and bicomponent magnonic waveguides are studied through the micromagnetic simulation. The magnonic waveguides composed of M and N stripes based on different values of saturation magnetization. In air-gap stripes magnonic waveguides, the air-gaps in N (i.e., Ms = 0) are sandwiched between the M of magnetic materials where the magnetostatic coupling take place due to the inhomogeneous field. In bicomponent magnonic waveguides(BMW), the exchange interaction is dominant due to the presence of two magnetic materials (M and N stripes). The exchange interaction plays a major role in BMW existing at the interfaces of different magnetic materials which enhance the SWs propagation. Air - gap stripes based magnonic waveguides exhibit the transmission bands in range of ≈ 3-5 GHz and bicomponent exhibits ≈ 14-39 GHz, respectively. This work paves the way to develop the narrow and wide transmission bands based on magnonic waveguide which is suitable for signal transmission and processing devices. [ABSTRACT FROM AUTHOR]

In the Micromagnetic study, current induced magnetization precession dynamics led by Spin Transfer Torque [STT] in a Spin Valve Device [SVD] is investigated numerically by solving the Landau Lifshitz Gilbert Slonczewski [LLGS] equation via Object Oriented Micro Magnetic Framework [OOMMF]. The bottom and top ferromagnetic layers are made of Ferro-Magnetic Alloy [FMA] called EuO (i.e.) a europium chalcogenide. Here, we have introduced the Current Induced Oersted Field [CIOF] and it is generated when the spin polarized current passes through the SVD. By varying the generated Oersted Field [OF] strength (Hoe) from 0 kA/m to 30 kA/m, as an increment of 10 kA/m the frequency tunability is achieved. The result imputes that, if we increase the OF strength from 0 kA/m to 30 kA/m frequency keeps on increasing, but the PSD reduces. At 0 kA/m (in the absence of the OF), 27 GHz frequency with 0.042 (arb. unit) is obtained. On the other hand, at 30 kA/m (in the presence of the OF), 34 GHz frequency with 0.021 (arb. unit) is obtained. The obtained results shown here promote the future application of SVD in spintronic devices. [ABSTRACT FROM AUTHOR]

In the present study, we have theoretically modeled a heterogeneous Tilted Polarizer [TP] based Spin Torque Nano Oscillator [STNO] with two independent variables (β & θ). The magnetization precession dynamics led by Spin Transfer Torque [STT] is numerically studied by solving the Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. Here, β & θ are the TP angle and the angle between free layer magnetization and the easy axis of the device respectively. Both β & θ can be varied from 0° to 90°. For every particular β, we varied the θ from 10° to 90°. It is ostensibly visible that in all the tilt angles, the frequency is accessible and highly tunable in the order of GHz. The maximum frequency of the device is obtained at β = 60° & θ = 90°. The obtained frequency is 227 GHz and PSD of 1.719 µW/mA2/GHz with a solid current density of 8 × 1010 A/m2 with a zero applied field. To the best of the author's knowledge, we have reported the maximum frequency emitted by a single STNO of about 227 GHz, which is highly applicable for Extremely-High-Frequency applications. It opens a new door for the clutter breaking innovations in the field of spin based electronics. [ABSTRACT FROM AUTHOR]

The current induced magnetization precession dynamics by Spin Transfer Torque [STT] in a Spin Torque Nano Oscillator [STNO] device is investigated numerically by solving the Landau Lifshitz Gilbert Slonczewski [LLGS] equation. In the present study, we have devised a Heterogeneous based STNO device made of Ferro Magnetic [FM] Alloy. The base layer is made of Fe85B13Ni2 and the apex layer is made of Co2Fe0.4Mn0.6Si. The copper acts as a Non-Magnetic [NM] spacer. We have introduced the Current Induced Oersted Field [CIOF] and it is generated when the spin polarized current passes through the device. By varying the generated Oersted Field [OF] strength (Hoe) from 0 kA/m to 50 kA/m, as an increment of 10 kA/m the frequency tunability is achieved. The result imputes that, if we increase the OF strength from 0 kA/m to 50 kA/m frequency keeps on increasing, but the Power reduces. At 0 kA/m (in the absence of the OF), 26.36 GHz frequency with 6.116 (nW/mA2/GHz) is obtained. On the other hand, at 50 kA/m (in the presence of the OF), 115.9 GHz frequency with 2.105 (nW/mA2/GHz) is obtained. The author insinuates that the results are applicable for nanoscale spintronic devices in Extremely High-Frequency applications. [ABSTRACT FROM AUTHOR]

The present work deals with the theoretical modeling of Spin Hall Spin Torque Nano Oscillator (SHSTNO) using four different Ferromagnetic Materials (FM) (Py, Co, CoFeB and Ni) with Current In Plane (CIP) geometry. The device comprised of bilayer (Pt/X) (i.e.)a top Ferromagnetic Free Layer (FFL) which is notated as (X) along with the heavy metal (Pt). In this work, we tried to tune the frequency of the device by using different materials in FFLand by altering the Spin Hall Angle (SHA), which is notated as (θ). The sustained oscillation in the FFL is studied by the governing LandauLifshitz-Gilbert-Slonczewski (LLGS) equation. The device works under the principle called Spin Hall Effect (SHE) that originates from spin-orbit scattering paves for the deflection of conduction electrons with opposite signs oriented in the opposite direction. When the spin reaches FFL due to the phenomena called Spin Transfer Torque (STT), persistent oscillation occurs, resulting in the emission of frequency in the microwave regime. The SHA (θ) is highly tunable up to 0.8 from 0.1. The author mentions that one can vary (θ) to the maximum and use the low Saturation Magnetization (SM) based material in FFL for maximum frequency tunability. The results presented in the article can find the application as spinwave emitters for magnonic applications where the spin waves may use for transmission and processing information. [ABSTRACT FROM AUTHOR]

In the present work, we have reported the results based on the effect of Bi-Quadratic Coupling [BQC] as well as the Orange Peel Coupling [OPC] in different Heterogeneous based Spin Torque Nano Oscillator [STNO] device. STNO, comprised of trilayer (X/Cu/Py) (i.e) two ferromagnetic layers separated by a non magnetic spacer. Those Ferro Magnetic [FM] layers are called fixed and free, because the corresponding magnetization tends to be fixed and free. Throughout the macro magnetic framework, Cu is taken as the non magnetic spacer and Py is taken in free layer. X (= Fe and Co) denotes the FM taken in the pinned layer for both the BQC and OPC coupling mechanism. The magnetization switching dynamics of the free layer for all devices are studied by solving the governing Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. For all the four devices, switching time is calculated in the presence and absence of both BQC and OPC separately. The switching time for BQC based device [Co/Cu/Py] is calculated as 136 ps and 166 ps in the presence and absence respectively. Similar results are found in another BQC based device [Fe/Cu/Py]. The calculated switching time for the device is 135 ps and 181 ps in the presence and absence respectively. As far as the OPC is concerned, the switching time for the device [Co/Cu/Py] is found to be 111 ps and 160 ps in the presence and absence respectively. Relatively, other OPC based device [Fe/Cu/Py] switches 113 ps and 163 ps in the presence and absence respectively. The results depicts that OPC based devices switches rapidly as compared to BQC based devices which are highly applicable in ultra high density recording media. [ABSTRACT FROM AUTHOR]

We theoretically modelled a couple of Spin Hall Spin Torque Nano Oscillator [SHSTNO] with Current In Plane [CIP] Geometry. In general, the device comprised of bilayer (i.e.) a Ferro magnetic free layer [Co and CoFeB] along with the heavy metal [Pt]. The main motto of the present study is to tune the frequency of the above mentioned devices by altering the Spin Hall Angle [SHA] (θ). The sustained oscillation in the oscillating free layer is studied by the governing Landau-Lifshitz-Gilbert- Slonczewski [LLGS] equation. The devices mainly works under the principle of Spin Hall Effect [SHE], which originates from spin orbit scattering paves for the deflection of conduction electrons with opposite signs oriented in opposite direction. When the spin reaches the free layer due to the Spin Transfer Torque phenomena [STT], persistent oscillation occurs which end up in emitting the microwave frequency. Those are highly tunable with the aid of (θ), which generally varies from 0.1 to 0.9. The author sparks that for maximum frequency tunability, one can easily vary the SHA, (θ) to the maximum with the free layer of minimal thickness paves for the maximum frequency emission by the device. For CoFeB device, at free layer thickness of about 3 nm and the corresponding SHA of about 0.8, the maximum frequency of 67.8 GHz is obtained. The author emphasize that, the results shown here can find the application as spin wave emitters for magnonic applications where the spin waves are used for transmission and processing information on nano scale level. [ABSTRACT FROM AUTHOR]

In this micromagnetic framework, Spin transfer torque induced magnetization switching in Co/Cu/Co nanopillar device is investigated numerically. The magnetization switching dynamics of the free layer in the nanopillar device is governed by the Landau Lifshitz Gilbert Slonczewski (LLGS) equation and solving it numerically by employing OOMMF, a micromagnetic software. Results are obtained by varying the fixed layer orientation (β) of our nanopillar device from in-plane to out-of-plane (i.e.) from 0° to 80° and the corresponding switching time is noted. Results of the micromagnetic simulation reveals that there is an extreme reduction of switching time in the free layer of our devised nanopillar, if we increase the fixed layer angle (β) from 0° to 80°. The corresponding switching time got shortened from 1651 picoseconds to 104.44 picoseconds and is obtained for an applied current density of 2.25×1011Am-2 with 0.05 T as applied bias field. For 90° (i.e.) out-of-plane orientation, the magnetization switching is not exist, because the free layer magnetization follows an oscillation state. Moreover, when we compare 0° to 80°, the switching time is reduced almost 16 times which solely provoked as a source of future spintronic devices for magnetic storage applications. [ABSTRACT FROM AUTHOR]

Spin waves in ID periodic triangular array of antidots are encarved in a permalloy magnonic waveguide is investigated through micromagnetic simulation. The effect of the rotating array of antidots and in-plane rotation of the scattering centers on the band structure are investigated, to indicate new possibilities of fine tuning of spin-wave filter pass and stop bands. The results show that, the opening and closing of band gaps paves a way for band pass and stop filters on waveguide. From the results, the scattering center and strong spatial distribution field plays crucible role for controlling opening and closing bandgap width of ∼12 GHz for 0° rotation. We have obtained a single narrow bandgap of width 1GHz is obtained for 90° rotation of the antidot. Similarly, the tunability is achieved for desired microwave applications done by rotating triangular antidots with different orientation. [ABSTRACT FROM AUTHOR]

We theoretically study the dynamics of a field induced domain wall in the Py/Pt bi-layer structure in the presence of spin-Hall effect (SHE) by solving the Landau-Lifshitz-Gilbert (LLG) equation along with the adiabatic, nonadiabatic and SHE spin-transfer torques (STTs). It is observed that a weak magnetic field moves the domain wall with high velocity in the presence of SHE and the direction of the velocity is changed by changing the direction of the weak field. The numerical results show that the magnetization of the ferromagnetic layer can be reversed quickly through domain wall motion by changing the direction of a weak external field in the presence of SHE while the direction of current is fixed. The SHE reduces the magnetization reversal time of 1000 nm length strip by 14.7 ns. This study is extended to model a domain wall based GMR (Giant Magnetoresistance) read head with SHE. [ABSTRACT FROM AUTHOR]

We have studied the effect of biquadratic coupling (BQC) on critical current density in the Co/Cu/Ni-Fe nanopillar by solving the magnetization switching dynamics of the free layer which is governed by Landau- Lifshitz-Gilbert-Slonczewski (LLGS) equation. The LLGS equation is analytically solved for the time independent case and value of the critical current density required to initiate the magnetization switching is calculated. Its value in the absence of BQC is 0.8576 × 1012Am-2 and in the presence of BQC its value increases to 1.0914 × 1012Am-2. BQC field is acting along the easy axis which opposes the free layer magnetization moving to the out of plane and hence the value of critical current density is high in the presence of BQC. We can reduce the critical current density by reducing the BQC field which can be achieved by making the nanopillar with minimal or no roughness in the pinned and free layer. [ABSTRACT FROM AUTHOR]

Magnetization switching driven by spin transfer torque in a ferromagnetic nanopillar by biasing the angular polarizer with different orientation has been studied. The free layer dynamics includes the spin torque from the oscillating free layer with magneto crystalline anisotropy and shape anisotropy, which is governed by the Landau-Lifshitsz-Gilbert-Slonczweski (LLGS) equation and solving it numerically by using embedded Runge Kutta fourth order method. Results of numerical simulation shows that there is a drastic reduction of switching time in the free layer by the orientation of angular polarizer of the nano pillar device. We fixed the angular polarizer as 0°, 30°, 60°, 90° and the corresponding switching time is 6.53 ns, 4.36 ns, 2.25 ns and 1.21 ns respectively for an applied current density of 5 × 1011 Am-2. [ABSTRACT FROM AUTHOR]

Nonlinear localized magnetic excitation in a periodic array of ferromagnetic alloy is investigated by applying periodic magnetic field of spatially varying strength. The governing Landau-Lifshitz (LL) equation is transformed into variable coefficient nonlinear Schrödinger (VCNLS) equation using stereographic projection. By using similarity transformation technique and with certain integrability conditions, the VCNLS equation is reduced to standard Nonlinear Schrödinger (NLS) equation. The solution of VCNLS equation is obtained by using the known bright and dark soliton solutions of the standard NLS equation provided the VCNLS equation must satisfy the integrability conditions. The results suggest a way to control the dynamics of magnetization of the periodic array of ferromagnetic alloy structure in the form of soliton by choosing the suitable ferromagnetic alloys which satisfies the integrability conditions. From the obtained soliton solutions, it is found that by choosing different combination of ferromagnetic alloys to form a periodic composite ferromagnetic structure one can control the amplitude and width of the soliton solution. [ABSTRACT FROM AUTHOR]

The article mainly focuses on the enrichment of the output power obtained from Spin torque nano-oscillator by introducing the heterogeneous structure in multilayer nanopillar device. Here we devised two homogeneous and two heterogeneous devices having NiFe and Co materials. The dynamics of the devices are governed by a famous Landu-Lifshitz -Gilbert-Slonczewski (LLGS) equation which can be solved numerically using embedded RK-4 procedure. The current density and the external magnetic field for four devices are taken as 5x1011A/m2 and 6x10-3 A/m respectively. The applied dc current is converted into spin polarized dc current while it passes through pinned layer. The generated spin polarized dc currents produces spin transfer torque with the free layer magnetization via spacer. Thus the magnetization of the free layer gets a sustained oscillation. The results obtained from the heterogeneous STNOs are really fascinating. The frequency of the NiFe/Cu/NiFe and Co/Cu/NiFe devices have the same frequency but there is a tremendous change in the output power which is exactly twice that the NiFe/Cu/NiFe device. The similar behaviour is also obtained from Co/Cu/Co and NiFe/Cu/Co devices. The line width and the Q-factor of the output microwave signal are also computed. Among the four devices, the NiFe/Cu/Co heterogeneous device has low line width (408 MHz) and high Q-factor (4.77). [ABSTRACT FROM AUTHOR]

The effect of biquadratic coupling on spin current induced magnetization switching in a Co/Cu/Ni-Fe nanopillar device is investigated by solving the free layer magnetization switching dynamics governed by the Landau- Lifshitz-Gilbert-Slonczewski (LLGS) equation. The LLGS equation is numerically solved by using Runge-Kutta fourth order procedure for an applied current density of 5 × 1012Am-2. Presence of biquadratic coupling in the ferromagnetic layers reduces the magnetization switching time of the nanopillar device from 61 ps to 49 ps. [ABSTRACT FROM AUTHOR]

In this article, we have theoretically devised a Spin Torque Nano Oscillator (STNO) with perpendicular polarizer using macro spin model. The devised spin valve structure is heterogeneous (i.e.) it is made of two different ferromagnetic materials [Co and its alloy CoFeB]. The dynamics of magnetization provoked by spin transfer torque is studied numerically by solving the famous Landau-Lifshitz-Gilbert-Slonczewski [LLGS] equation. The results are obtained for the perpendicular polarizer and for that particular out of plane orientation we vary the free layer angle from 10° to 90°. The obtained results are highly appealing, because frequency range is available in all the tilt angles of free layer and it is exceptionally tunable in all free layer tilt angles with zero applied field. Moreover, the utmost operating frequency of about 83.3 GHz and its corresponding power of 4.488 µW/mA2/GHz is acquired for the free layer tilt angle θ = 90° with the solid applied current density of 10 × 1010 A/m2. Also, our device emits high quality factor of about 396, which is remarkably desirable for making devices. These pioneering results provides a significant development for future spintronic based devices. [ABSTRACT FROM AUTHOR]

We investigate nonlinear localized magnetic excitations in a simple form of one dimensional magnonic crystal by considering a ferromagnetic medium under periodic applied magnetic field of spatially varying strength. The governing Landau-Lifshitz equation is transformed into nonlinear evolution equation of a complex function through stereographic projection technique. The associated evolution equation numerically solved by using split-step Fourier method (SSFM). From the obtained results it is observed that the excitations appear in the form of solitons and the periodic magnetic field of spatially varying strength perturbs the soliton propagation. Bright and dark soliton solutions are constructed and studied the effect of tuning the strength of spatially periodic applied magnetic field on the nonlinear excitation of magnetization. The results show that the amplitude and velocity of the soliton can be effectively managed by varying the strength of spatially periodic applied magnetic field and it act as periodic potential which provides an additional degree of freedom to control the nature of soliton propagation in a ferromagnetic medium. [ABSTRACT FROM AUTHOR]

Spin wave (SW) propagation in 1-D magnonic antidot waveguides (MAWs) having different width w modulation of square shaped antidots studied through the micromagnetic simulation. The varying width modulation on square antidots affects the spin wave propagation in the waveguide. The inhomogeneity of the demagnetization field will increases when the width w of antidots increases, due to the Bragg's reflection of SW takes place along the width direction. Hence, the wider width of the second bandgap can be achieved, such as (II: 7.09 GHz) and (II: 19.29 GHz) for [12 12] and [12 18]. The achieved two bandgaps (I) and (II) are direct ones, and their origins can be understood through the spatial distribution profiles of power and phase (PPDPs) in the waveguides. This work paves the way to develop efficient SW filters based on MAWs at the nanoscale, which is highly useful in microwave communications. [ABSTRACT FROM AUTHOR]

The present work deals with the modeling of Homogeneous (Homo) as well as Heterogeneous (Hetero) Magneto Resistance based Perpendicular Polarizer Spin Torque Nano Oscillator (MR-PP STNO) through macro magnetic framework. The numerically modeled MR- PP STNO is of trilayer structure, (i.e.) a nonmagnetic spacer, sandwiched between a couple of Ferro Magnetic (FM) layers. If both FM in the device are same (Co) then it is called Homo MR-PP STNO, whereas both FM in the device is different (Co and Py), then it is called Hetero MR-PP STNO. The magnetization dynamics of both the devices are numerically studied by solving the Landau Lifshitz Gilbert Slonczewski (LLGS) equation. The results are acquired by varying Tilted Free Layer (TFL) (θ) from 10o to 90o as an increment of 10°. From the results, it is evident that the frequency and power keep on increasing if we increase the TFL from 10° to 90° for both devices. Also, the frequency and power of both devices are accessible in all the TFL with zero applied field. The maximum frequency of about 63 GHz with the corresponding power of 4.75 ((μW/mA2)/GHz) is obtained for Hetero based MR-PP STNO with TFL (θ) as 90°. The author mentions that the results shown here are highly significant in the development of forthcoming spin-based electronics. [ABSTRACT FROM AUTHOR]