Magnetic properties of CoFeB films in the ultrathin limit
Oral-In-person
Abstract
In magnetic memory applications, among the critical material parameters that impact device performance are the magnetic moment, the magnetic anisotropy, the Gilbert damping, and the Heisenberg exchange parameter. The Heisenberg exchange is one quantity for which there has been disagreement about how to obtain reliable values in ultrathin films.
In this work, we use Brillouin light scattering (BLS) measurements to map the spin wave manifold of ultrathin CoFeB films to determine the Heisenberg exchange parameter. This method is an extension of previous BLS measurements on thicker films [1]. For films with thicknesses ranging from 1.1 to 1.9 nm, we obtain values of the exchange parameter Aex ranging from approximately 0.5–10 pJ/m (compare to bulk value of ~27.5 pJ/m [2]) and observe a trend where Aex decreases with film thickness. We also determine the exchange parameter using magnetometry and compare to our BLS measurements. Our work establishes a method for determining the exchange parameter in application-relevant ultrathin films and demonstrates that it can deviate significantly from the bulk value in the ultrathin limit.
1. Riley et al., Appl. Phys. Lett., Vol. 120, p.112405 (2020)
2. Devolder et al., J. Appl. Phys., Vol. 120, p.183902 (2016)
In this work, we use Brillouin light scattering (BLS) measurements to map the spin wave manifold of ultrathin CoFeB films to determine the Heisenberg exchange parameter. This method is an extension of previous BLS measurements on thicker films [1]. For films with thicknesses ranging from 1.1 to 1.9 nm, we obtain values of the exchange parameter Aex ranging from approximately 0.5–10 pJ/m (compare to bulk value of ~27.5 pJ/m [2]) and observe a trend where Aex decreases with film thickness. We also determine the exchange parameter using magnetometry and compare to our BLS measurements. Our work establishes a method for determining the exchange parameter in application-relevant ultrathin films and demonstrates that it can deviate significantly from the bulk value in the ultrathin limit.
1. Riley et al., Appl. Phys. Lett., Vol. 120, p.112405 (2020)
2. Devolder et al., J. Appl. Phys., Vol. 120, p.183902 (2016)
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Presenters
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William Peria
- National Institute of Standards and Technology (NIST)