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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) Schematic illustration of ion beam irradiation of a bilayer circular structure. (b) TR-MOKE trace from a sample irradiated with ion dose d = 3.1 pC/μm2. Note changes in the time base. (c) Time-resolved Kerr images of the sample at three time delays.
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f1: (a) Schematic illustration of ion beam irradiation of a bilayer circular structure. (b) TR-MOKE trace from a sample irradiated with ion dose d = 3.1 pC/μm2. Note changes in the time base. (c) Time-resolved Kerr images of the sample at three time delays.

Mentions: A bilayer of NiFe(10 nm)/Pt(3 nm) was grown by sputtering on a thermally oxidised Si[100] substrate using a ultrahigh vacuum deposition system from a base pressure ~1 × 10−8 Torr. The bilayer films were patterned by electron beam lithography into 30 μm disks and were irradiated with irradiation dose (d) varying from 0 to 3.3 pC/μm2. Figure 1(a) shows a schematic diagram of the sample. NiFe was chosen for its negligible anisotropies. Pt was selected as an important heavy metal with regard to its strong spin-orbit coupling23 and significant proximity induced magnetic moment, although the role of this is currently an open question. Structurally, the as-deposited NiFe/Pt interface is shown to have a typical width of less than 1 nm, resulting form a combination of topological roughness and chemical intermixing as obsrved here by x-ray reflectivity. It has been shown in a previous detailed structural study of NiFe/Au that with higher ion dose the interface rapidly becomes broader, the capping layer becomes very thin and the layer develops into a compositionally-graded alloy due to the intermixing of atoms of the heavy NM layer into the FM layer2425. Pt also forms a protective layer preventing the oxidation of the NiFe.


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) Schematic illustration of ion beam irradiation of a bilayer circular structure. (b) TR-MOKE trace from a sample irradiated with ion dose d = 3.1 pC/μm2. Note changes in the time base. (c) Time-resolved Kerr images of the sample at three time delays.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (a) Schematic illustration of ion beam irradiation of a bilayer circular structure. (b) TR-MOKE trace from a sample irradiated with ion dose d = 3.1 pC/μm2. Note changes in the time base. (c) Time-resolved Kerr images of the sample at three time delays.
Mentions: A bilayer of NiFe(10 nm)/Pt(3 nm) was grown by sputtering on a thermally oxidised Si[100] substrate using a ultrahigh vacuum deposition system from a base pressure ~1 × 10−8 Torr. The bilayer films were patterned by electron beam lithography into 30 μm disks and were irradiated with irradiation dose (d) varying from 0 to 3.3 pC/μm2. Figure 1(a) shows a schematic diagram of the sample. NiFe was chosen for its negligible anisotropies. Pt was selected as an important heavy metal with regard to its strong spin-orbit coupling23 and significant proximity induced magnetic moment, although the role of this is currently an open question. Structurally, the as-deposited NiFe/Pt interface is shown to have a typical width of less than 1 nm, resulting form a combination of topological roughness and chemical intermixing as obsrved here by x-ray reflectivity. It has been shown in a previous detailed structural study of NiFe/Au that with higher ion dose the interface rapidly becomes broader, the capping layer becomes very thin and the layer develops into a compositionally-graded alloy due to the intermixing of atoms of the heavy NM layer into the FM layer2425. Pt also forms a protective layer preventing the oxidation of the NiFe.

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