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Title: Broadband Spectroscopy of Thermodynamic Magnetization Fluctuations through a Ferromagnetic Spin-Reorientation Transition

Abstract

We use scanning optical magnetometry to study the broadband frequency spectra of spontaneous magnetization fluctuations, or “magnetization noise,” in an archetypal ferromagnetic film that can be smoothly tuned through a spin-reorientation transition (SRT). The SRT is achieved by laterally varying the magnetic anisotropy across an ultrathin Pt / Co / Pt trilayer, from the perpendicular to in-plane direction, via graded Ar + irradiation. In regions exhibiting perpendicular anisotropy, the power spectrum of the magnetization noise S ( ν ) exhibits a remarkably robust ν - 3 / 2 power law over frequencies ν from 1 kHz to 1 MHz. As the SRT region is traversed, however, S ( ν ) spectra develop a steadily increasing critical frequency ν 0 , below which the noise power is spectrally flat, indicating an evolving low-frequency cutoff for magnetization fluctuations. The magnetization noise depends strongly on applied in- and out-of-plane magnetic fields, revealing local anisotropies and also a field-induced emergence of fluctuations in otherwise stable ferromagnetic films. Finally, we demonstrate that higher-order correlators can be computed from the noise. These results highlight broadband spectroscopy of thermodynamic fluctuations as a powerful tool to characterize the interplay between thermal and magnetic energy scales, and as a means of characterizing phase transitions in ferromagnets.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE; LANL Laboratory Directed Research and Development (LDRD) Program; National Science Foundation (NSF)
OSTI Identifier:
1471805
Alternate Identifier(s):
OSTI ID: 1479988
Report Number(s):
LA-UR-18-22421
Journal ID: ISSN 2160-3308; PRXHAE; 031078
Grant/Contract Number:  
AC52-06NA25396; DMR-1157490
Resource Type:
Published Article
Journal Name:
Physical Review. X
Additional Journal Information:
Journal Name: Physical Review. X Journal Volume: 8 Journal Issue: 3; Journal ID: ISSN 2160-3308
Publisher:
American Physical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; High Magnetic Field Science

Citation Formats

Balk, A. L., Li, F., Gilbert, I., Unguris, J., Sinitsyn, N. A., and Crooker, S. A. Broadband Spectroscopy of Thermodynamic Magnetization Fluctuations through a Ferromagnetic Spin-Reorientation Transition. United States: N. p., 2018. Web. https://doi.org/10.1103/PhysRevX.8.031078.
Balk, A. L., Li, F., Gilbert, I., Unguris, J., Sinitsyn, N. A., & Crooker, S. A. Broadband Spectroscopy of Thermodynamic Magnetization Fluctuations through a Ferromagnetic Spin-Reorientation Transition. United States. https://doi.org/10.1103/PhysRevX.8.031078
Balk, A. L., Li, F., Gilbert, I., Unguris, J., Sinitsyn, N. A., and Crooker, S. A. Fri . "Broadband Spectroscopy of Thermodynamic Magnetization Fluctuations through a Ferromagnetic Spin-Reorientation Transition". United States. https://doi.org/10.1103/PhysRevX.8.031078.
@article{osti_1471805,
title = {Broadband Spectroscopy of Thermodynamic Magnetization Fluctuations through a Ferromagnetic Spin-Reorientation Transition},
author = {Balk, A. L. and Li, F. and Gilbert, I. and Unguris, J. and Sinitsyn, N. A. and Crooker, S. A.},
abstractNote = {We use scanning optical magnetometry to study the broadband frequency spectra of spontaneous magnetization fluctuations, or “magnetization noise,” in an archetypal ferromagnetic film that can be smoothly tuned through a spin-reorientation transition (SRT). The SRT is achieved by laterally varying the magnetic anisotropy across an ultrathin Pt/Co/Pt trilayer, from the perpendicular to in-plane direction, via graded Ar+ irradiation. In regions exhibiting perpendicular anisotropy, the power spectrum of the magnetization noise S(ν) exhibits a remarkably robust ν-3/2 power law over frequencies ν from 1 kHz to 1 MHz. As the SRT region is traversed, however, S(ν) spectra develop a steadily increasing critical frequency ν0, below which the noise power is spectrally flat, indicating an evolving low-frequency cutoff for magnetization fluctuations. The magnetization noise depends strongly on applied in- and out-of-plane magnetic fields, revealing local anisotropies and also a field-induced emergence of fluctuations in otherwise stable ferromagnetic films. Finally, we demonstrate that higher-order correlators can be computed from the noise. These results highlight broadband spectroscopy of thermodynamic fluctuations as a powerful tool to characterize the interplay between thermal and magnetic energy scales, and as a means of characterizing phase transitions in ferromagnets.},
doi = {10.1103/PhysRevX.8.031078},
journal = {Physical Review. X},
number = 3,
volume = 8,
place = {United States},
year = {2018},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1103/PhysRevX.8.031078

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Cited by: 2 works
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Figures / Tables:

FIG. 1. FIG. 1.: (a) Experimental schematic. A scanning broadband optical magnetometer based on polar MOKE measures the spontaneously fluctuating out-of-plane magnetizationmore » $\delta$$m$$z$ within a small (4 $μ$m) spot on the sample. The power spectral density of this magnetization noise $S$($ν$) is continuously computed and averaged in real time (PBS: polarizing beamsplitter, FFT: fast Fourier transform). The sample is a Pt/Co/Pt trilayer irradiated with a laterally varying dose of Ar+, generating a lateral gradient of interfacial magnetic anisotropy. Red and blue colors depict Co and Pt layers; arrows depict the net magnetization direction, with yellow arrows indicating the region where the spin reorientation transition (SRT) occurs. (b) The magnetic contrast image of the trilayer surface (adapted from Ref. [32]) shows the mazelike domain patterns that form in graded trilayers of this type. The patterns become blurry near the SRTas fluctuations increase and occur faster than the image acquisition time. Conventional MOKE magnetization measurements $m$$z$($B$$z$) show that the coercive field $μ$0$H$$c$ → 0 as the SRT is approached. (c) Characteristic Kerr rotation fluctuations $\delta$θ$K$($t$) reveal the thermodynamic magnetization fluctuations $\delta$$m$$z$($t$). (d) $S$($ν$) falls as a $ν$−3/2 power law over the measured 1 kHz–1 MHz range in regions of the trilayer exhibiting perpendicular magnetization. Discussion of measurement uncertainties in this and subsequent figures can be found in the Supplemental Material [35].« less

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Works referenced in this record:

Noise of ferromagnetic materials
journal, September 1969


Higher-order spin noise statistics
journal, November 2013


Ferromagnetic strip domains in an atomic monolayer
journal, November 1988


Real-time observation of domain fluctuations in a two-dimensional magnetic model system
journal, April 2015

  • Kronseder, M.; Meier, T. N. G.; Zimmermann, M.
  • Nature Communications, Vol. 6, Issue 1
  • DOI: 10.1038/ncomms7832

Monitoring superparamagnetic Langevin behavior of individual SrRuO 3 nanostructures
journal, January 2014


Domain‐wall dynamics and Barkhausen effect in metallic ferromagnetic materials. I. Theory
journal, September 1990

  • Alessandro, Bruno; Beatrice, Cinzia; Bertotti, Giorgio
  • Journal of Applied Physics, Vol. 68, Issue 6
  • DOI: 10.1063/1.346423

Stripe domains morphology versus layers thickness in CoPt multilayers
journal, April 1997

  • Belliard, L.; Miltat, J.; Kottler, V.
  • Journal of Applied Physics, Vol. 81, Issue 8
  • DOI: 10.1063/1.364531

Dynamic fluctuations and two-dimensional melting at the spin reorientation transition
journal, September 2012


White-noise magnetization fluctuations in magnetoresistive heads
journal, March 2001

  • Smith, Neil; Arnett, Patrick
  • Applied Physics Letters, Vol. 78, Issue 10
  • DOI: 10.1063/1.1352694

Domains in perpendicularly magnetized ultrathin films studied using the magnetic susceptibility
journal, October 1999


Spectroscopy of spontaneous spin noise as a probe of spin dynamics and magnetic resonance
journal, September 2004

  • Crooker, S. A.; Rickel, D. G.; Balatsky, A. V.
  • Nature, Vol. 431, Issue 7004
  • DOI: 10.1038/nature02804

Planar Patterned Magnetic Media Obtained by Ion Irradiation
journal, June 1998


Asymmetric magnetic domain-wall motion by the Dzyaloshinskii-Moriya interaction
journal, December 2013


Cone phase and magnetization fluctuations in Au/Co/Au thin films near the spin-reorientation transition
journal, July 2010


Modulation of the magnetic domain size induced by an electric field
journal, July 2016

  • Ando, F.; Kakizakai, H.; Koyama, T.
  • Applied Physics Letters, Vol. 109, Issue 2
  • DOI: 10.1063/1.4955265

Tailoring magnetism by light-ion irradiation
journal, July 2004


Spin Noise of Electrons and Holes in Self-Assembled Quantum Dots
journal, January 2010


The fluctuation-dissipation theorem
journal, January 1966


Asymmetry of the spin reorientation transition in ultrathin Fe films and wedges grown on Ag(100)
journal, February 1993


Observation of 1/ƒ magnetic fluctuations in spin glasses
journal, February 1986


Reversible transition between perpendicular and in-plane magnetization in ultrathin films
journal, June 1990


Spin Noise Spectroscopy in GaAs
journal, November 2005


Observation of Stripe Mobility in a Dipolar Frustrated Ferromagnet
journal, February 2006


Quantification of thermal fluctuations in stripe domain patterns
journal, February 2016


Direction of the magnetization of thin films and sandwiches as a function of temperature
journal, July 1990


Magnetization fluctuations in uniformly magnetized thin-film recording media
journal, January 1990

  • Silva, T. J.; Bertram, H. N.
  • IEEE Transactions on Magnetics, Vol. 26, Issue 6
  • DOI: 10.1109/20.102901

1 f noise and other slow, nonexponential kinetics in condensed matter
journal, April 1988


Magnetic Stripe Domains in Coupled Magnetic Sandwiches
journal, September 2004


Dynamics of a Ferromagnetic Domain Wall and the Barkhausen Effect
journal, December 1997


Nonequilibrium spin noise and noise of susceptibility
journal, November 2014


Dynamics of Dzyaloshinskii domain walls in ultrathin magnetic films
journal, December 2012


What is a spin glass? A glimpse via mesoscopic noise
journal, July 1993


Reorientation transitions in ultrathin ferromagnetic films by thickness- and temperature-driven anisotropy flows
journal, August 1996


Dipolar-energy-activated magnetic domain pattern transformation driven by thermal fluctuations
journal, June 2013

  • Kronseder, M.; Buchner, M.; Bauer, H. G.
  • Nature Communications, Vol. 4, Issue 1
  • DOI: 10.1038/ncomms3054

Magnetic Noise in Structured Hard Magnets
journal, January 2010


Magnetism in ultrathin film structures
journal, April 2008


Statistical properties of Barkhausen noise in amorphous ferromagnetic films
journal, September 2014


Self-Similar Barkhausen Noise in Magnetic Domain Wall Motion
journal, October 1996


Linear processes that produce 1/ f or flicker noise
journal, April 1995


Tracking Random Walk of Individual Domain Walls in Cylindrical Nanomagnets with Resistance Noise
journal, August 2010


Magnetic Bubble Domain Phase at the Spin Reorientation Transition of Ultrathin Fe / Ni / Cu ( 001 ) Film
journal, May 2007


Two-dimensional higher order noise spectroscopy up to radio frequencies
journal, December 2010

  • Starosielec, Sebastian; Fainblat, Rachel; Rudolph, Jörg
  • Review of Scientific Instruments, Vol. 81, Issue 12
  • DOI: 10.1063/1.3504369

Superparamagnetism
journal, April 1959

  • Bean, C. P.; Livingston, J. D.
  • Journal of Applied Physics, Vol. 30, Issue 4
  • DOI: 10.1063/1.2185850

Optical Spectroscopy of Spin Noise
journal, April 2013


Critical behavior of zero-field magnetic fluctuations in perpendicularly magnetized thin films
journal, November 2014


Perpendicular versus in-plane magnetization in a 2D Heisenberg monolayer at finite temperatures
journal, November 1990


Magnetic anisotropy in metallic multilayers
journal, November 1996

  • Johnson, M. T.; Bloemen, P. J. H.; Broeder, F. J. A. den
  • Reports on Progress in Physics, Vol. 59, Issue 11
  • DOI: 10.1088/0034-4885/59/11/002

Magnetization direction switching in Fe/Cu(100) epitaxial films: Temperature and thickness dependence
journal, December 1992


Noise in disordered systems: The power spectrum and dynamic exponents in avalanche models
journal, November 2000


Magnetic Stochastic Oscillators: Noise-Induced Synchronization to Underthreshold Excitation and Comprehensive Compact Model
journal, November 2015

  • Mizrahi, Alice; Locatelli, Nicolas; Matsumoto, Rie
  • IEEE Transactions on Magnetics, Vol. 51, Issue 11
  • DOI: 10.1109/TMAG.2015.2439736

Barkhausen pulse structure in an amorphous ferromagnet: Characterization by high-order spectra
journal, June 1998


Control of Magnetic Fluctuations by Spin Current
journal, September 2011


Magnetic stripe melting at the spin reorientation transition in Fe Ni Cu ( 001 )
journal, June 2005


Domain Structure in CoFeB Thin Films With Perpendicular Magnetic Anisotropy
journal, January 2011


    Works referencing / citing this record:

    Bubble Magnetometry of Nanoparticle Heterogeneity and Interaction
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    Detection and amplification of spin noise using scattered laser light in a quantum-dot microcavity
    journal, January 2020


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