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Tunable Magnetization Dynamics in Interfacially Modified Ni81Fe19/Pt Bilayer Thin Film Microstructures.

Ganguly A, Azzawi S, Saha S, King JA, Rowan-Robinson RM, Hindmarch AT, Sinha J, Atkinson D, Barman A - Sci Rep (2015)

Bottom Line: Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter.This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy.The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sec. III, Salt Lake, Kolkata 700098, India.

ABSTRACT
Interface modification for control of ultrafast magnetic properties using low-dose focused ion beam irradiation is demonstrated for bilayers of two technologically important materials: Ni81Fe19 and Pt. Magnetization dynamics were studied using an all-optical time-resolved magneto-optical Kerr microscopy method. Magnetization relaxation, precession, damping and the spatial coherence of magnetization dynamics were studied. Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter. A systematic study of the damping parameter and frequency as a function of irradiation dose varying from 0 to 3.3 pC/μm(2) shows a complex dependence upon ion beam dose. This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy. The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices.

No MeSH data available.


Related in: MedlinePlus

(a) FFT power spectra of the TR-MOKE data of ion irradiated NiFe/Pt samples at three different doses at H = 1.8 kOe. (b) Variation of frequency f as a function of dose at H = 1.8 kOe. Symbols are the experimental data and solid lines are linear fits. The shaded box represents the transion between two regions. (c) Magnetization relaxation times τ1 and τ2 are plotted as a function of dose. Here the symbols are obtained from experimental data while the solid lines are only guides to the eye.
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f4: (a) FFT power spectra of the TR-MOKE data of ion irradiated NiFe/Pt samples at three different doses at H = 1.8 kOe. (b) Variation of frequency f as a function of dose at H = 1.8 kOe. Symbols are the experimental data and solid lines are linear fits. The shaded box represents the transion between two regions. (c) Magnetization relaxation times τ1 and τ2 are plotted as a function of dose. Here the symbols are obtained from experimental data while the solid lines are only guides to the eye.

Mentions: Figure 4(a) shows FFT power spectra of the TR-MOKE data for three different doses. A clear decrease of f is observed with increasing dose. The variation of f with d is shown in Fig. 4(b). First a large decrease of f of 1.3 GHz occurs as d increases from 0.3 to 2.0 pC/μm2, while a smaller fall of 0.4 GHz occurs as d increases further from 2.0 to 3.3 pC/μm2. The literature43 shows a reduction of magnetic moment of Ni thin film with the concentration of Pt atoms. Hence, the decrease of f in region 1 is likely to be related to the reduction of moment due to the presence of Pt in the vicinity of Ni and Fe in the intermixed region. In region 2 a NiFe-Pt alloy is established throughout a large fraction of the original bilayer. The precessional frequency is almost constant with increasing dose, because the probability of sputtered Pt atoms to reach the pure NiFe layer by traversing through the thick interface region is small. This effect is in agreement with the structural evolution discussed earlier.


Tunable Magnetization Dynamics in Interfacially Modified Ni81Fe19/Pt Bilayer Thin Film Microstructures.

Ganguly A, Azzawi S, Saha S, King JA, Rowan-Robinson RM, Hindmarch AT, Sinha J, Atkinson D, Barman A - Sci Rep (2015)

(a) FFT power spectra of the TR-MOKE data of ion irradiated NiFe/Pt samples at three different doses at H = 1.8 kOe. (b) Variation of frequency f as a function of dose at H = 1.8 kOe. Symbols are the experimental data and solid lines are linear fits. The shaded box represents the transion between two regions. (c) Magnetization relaxation times τ1 and τ2 are plotted as a function of dose. Here the symbols are obtained from experimental data while the solid lines are only guides to the eye.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664935&req=5

f4: (a) FFT power spectra of the TR-MOKE data of ion irradiated NiFe/Pt samples at three different doses at H = 1.8 kOe. (b) Variation of frequency f as a function of dose at H = 1.8 kOe. Symbols are the experimental data and solid lines are linear fits. The shaded box represents the transion between two regions. (c) Magnetization relaxation times τ1 and τ2 are plotted as a function of dose. Here the symbols are obtained from experimental data while the solid lines are only guides to the eye.
Mentions: Figure 4(a) shows FFT power spectra of the TR-MOKE data for three different doses. A clear decrease of f is observed with increasing dose. The variation of f with d is shown in Fig. 4(b). First a large decrease of f of 1.3 GHz occurs as d increases from 0.3 to 2.0 pC/μm2, while a smaller fall of 0.4 GHz occurs as d increases further from 2.0 to 3.3 pC/μm2. The literature43 shows a reduction of magnetic moment of Ni thin film with the concentration of Pt atoms. Hence, the decrease of f in region 1 is likely to be related to the reduction of moment due to the presence of Pt in the vicinity of Ni and Fe in the intermixed region. In region 2 a NiFe-Pt alloy is established throughout a large fraction of the original bilayer. The precessional frequency is almost constant with increasing dose, because the probability of sputtered Pt atoms to reach the pure NiFe layer by traversing through the thick interface region is small. This effect is in agreement with the structural evolution discussed earlier.

Bottom Line: Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter.This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy.The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices.

View Article: PubMed Central - PubMed

Affiliation: Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sec. III, Salt Lake, Kolkata 700098, India.

ABSTRACT
Interface modification for control of ultrafast magnetic properties using low-dose focused ion beam irradiation is demonstrated for bilayers of two technologically important materials: Ni81Fe19 and Pt. Magnetization dynamics were studied using an all-optical time-resolved magneto-optical Kerr microscopy method. Magnetization relaxation, precession, damping and the spatial coherence of magnetization dynamics were studied. Magnetization precession was fitted with a single-mode damped sinusoid to extract the Gilbert damping parameter. A systematic study of the damping parameter and frequency as a function of irradiation dose varying from 0 to 3.3 pC/μm(2) shows a complex dependence upon ion beam dose. This is interpreted in terms of both intrinsic effects and extrinsic two-magnon scattering effects resulting from the expansion of the interfacial region and the creation of a compositionally graded alloy. The results suggest a new direction for the control of precessional magnetization dynamics, and open the opportunity to optimize high-speed magnetic devices.

No MeSH data available.


Related in: MedlinePlus