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Magnetic noise in structured hard magnets.
Zhu Diao1, E R Nowak, Gen Feng
1School of Physics and CRANN, Trinity College, Dublin 2, Ireland. diaoz@tcd.ie
Physical Review Letters
|April 7, 2010
Summary
Researchers studied magnetic noise in cobalt-iron/platinum multilayers. They found 1/f noise related to domain wall movement during magnetization reversal, offering insights into magnetic domain behavior.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Nanotechnology
Background:
- The anomalous Hall effect (AHE) is crucial for understanding magnetization dynamics in magnetic nanostructures.
- Multilayered thin films like (CoFe/Pt) exhibit complex magnetic domain structures and reversal processes.
- Characterizing magnetic noise provides insights into the microscopic mechanisms of magnetization reversal.
Purpose of the Study:
- To investigate the magnetization reversal process in (Co{90}Fe{10}/Pt){n} multilayer wires using the anomalous Hall effect.
- To identify the origins of magnetic noise and its relationship with domain wall dynamics.
- To analyze the frequency dependence and temporal evolution of magnetic noise.
Main Methods:
- Fabrication of multilayer wires with varying layer repetitions (10 ≤ n ≤ 50).
- Measurement of the anomalous Hall effect to probe magnetization.
- Analysis of time-independent 1/f noise and Barkhausen jumps in magnetic hysteresis.
- Characterization of domain wall motion and noise power spectrum.
Main Results:
- Time-independent 1/f noise was observed in samples with a quality factor Q<1 during continuous magnetization reversal.
- Magnetic noise is attributed to reversible excursions of domain wall segments (~100 nm).
- Barkhausen jumps occurred near switching and saturation fields, with noise power spectra following 1/f^1.7 and decaying over time.
Conclusions:
- The study reveals distinct noise signatures associated with different magnetization reversal regimes in CoFe/Pt multilayer wires.
- Reversible domain wall motion is a significant source of 1/f magnetic noise.
- Barkhausen jumps contribute to noise at field-dependent transitions, with characteristic power-law behavior.
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