Advances in Nanomagnets

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A:Physics".

Deadline for manuscript submissions: closed (30 June 2024) | Viewed by 966

Special Issue Editor


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Guest Editor
Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
Interests: nanomagnetism; magnetic nanostructure materials; spintronic devices and sensors; spin-dependent transport

Special Issue Information

Dear Colleagues,

Nanomagnets have been investigated and developed intensively with a focus on the unique properties of nanoscale magnetic materials. This Special Issue covers the recent advancements in and studies, both experimental and theoretical, on magnetic nanoparticles, nanowires, and thin film, as well as molecular magnets. Utilizing geometric confinement and physical proximity, novel nanomagnetic materials can be designed. Nanomagnetic structures exhibit wide applications in data storage, magnetic sensing, energy resources, quantum computing, and life science. Characterization techniques to probe the miniatured magnetic signal in unprecedented nanoscale structures have been developed and have enabled researchers to gain a better understanding of their fundamental physics and to create new materials with enhanced functionalities. Theoretical modeling and simulations in micromagnetics and magnetization dynamics also enable researchers to gain insights into the underlying physical process. All these advances in the field of nanomagnetics are highly interdisciplinary, drawing on expertise from materials science, physics, chemistry, engineering, and other fields, and are expected to continue to grow and evolve.

Dr. Ruihua Cheng
Guest Editor

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Keywords

  • nanomagnets
  • magnetic materials
  • magnetic nanoparticles
  • molecular magnets
  • micromagnetics
  • nanomagnetics
  • magnetization dynamics

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Published Papers (1 paper)

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Research

10 pages, 1790 KiB  
Article
Stress Engineering of Magnetization Fluctuation and Noise Spectra in Low-Barrier Nanomagnets Used as Analog and Binary Stochastic Neurons
by Rahnuma Rahman and Supriyo Bandyopadhyay
Micromachines 2024, 15(9), 1174; https://doi.org/10.3390/mi15091174 - 22 Sep 2024
Viewed by 629
Abstract
A single-domain nanomagnet, shaped like a thin elliptical disk with small eccentricity, has a double-well potential profile with two degenerate energy minima separated by a small barrier of a few kT (k = Boltzmann constant and T = absolute temperature). [...] Read more.
A single-domain nanomagnet, shaped like a thin elliptical disk with small eccentricity, has a double-well potential profile with two degenerate energy minima separated by a small barrier of a few kT (k = Boltzmann constant and T = absolute temperature). The two minima correspond to the magnetization pointing along the two mutually anti-parallel directions along the major axis of the ellipse. At room temperature, the magnetization fluctuates randomly between the two minima, mimicking telegraph noise. This makes the nanomagnet act as a “binary” stochastic neuron (BSN) with the neuronal state encoded in the magnetization orientation. If the nanomagnet is magnetostrictive, then the barrier can be depressed further by applying (electrically generated) uniaxial stress along the ellipse’s major axis, thereby gradually eroding the double-well shape. When the barrier almost vanishes, the magnetization begins to randomly assume any arbitrary orientation (not just along the major axis), making the nanomagnet act as an “analog” stochastic neuron (ASN). The magnetization fluctuation then begins to increasingly resemble white noise. The full width at half maximum (FWHM) of the noise auto-correlation function decreases with increasing stress, as the fluctuation gradually transforms from telegraph noise to white noise. Consistent with this trend, the noise spectral density exhibits a 1/fβ spectrum (at high frequencies) with β decreasing from 2.00 to 1.88 with increasing stress. Stress can thus not only reconfigure a BSN to an ASN, which has its own applications, but it can also perform “noise engineering”, i.e., tune the auto-correlation function and power spectral density, having applications in signal processing. Full article
(This article belongs to the Special Issue Advances in Nanomagnets)
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