Thermoinduced Magnetization in Nanoparticles of Antiferromagnetic Materials

Mørup, S.; Frandsen, Cathrine

doi:10.1103/physrevlett.92.217201

Cited by 107 publications

(75 citation statements)

References 30 publications

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“…A nonphysical temperature-dependent magnetic moment l p has been notably observed in nanoparticles by use of magnetometry, 39 where moments increase with increasing temperature. We previously have shown that the temperature-dependent magnetic moment in magnetometry may be rectified by abandoning a particle log-normal distribution of sizes and model the particles with a core moment and surface spins.…”

Section: Discussionmentioning

confidence: 99%

Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

Usselman

Russek

Klem

et al. 2012

Journal of Applied Physics

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Electron magnetic resonance (EMR) spectroscopy was used to determine the magnetic properties of maghemite (c-Fe 2 O 3 ) nanoparticles formed within size-constraining Listeria innocua (LDps)-(DNA-binding protein from starved cells) protein cages that have an inner diameter of 5 nm. Variable-temperature X-band EMR spectra exhibited broad asymmetric resonances with a superimposed narrow peak at a gyromagnetic factor of g % 2. The resonance structure, which depends on both superparamagnetic fluctuations and inhomogeneous broadening, changes dramatically as a function of temperature, and the overall linewidth becomes narrower with increasing temperature. Here, we compare two different models to simulate temperature-dependent lineshape trends. The temperature dependence for both models is derived from a Langevin behavior of the linewidth resulting from "anisotropy melting." The first uses either a truncated log-normal distribution of particle sizes or a bi-modal distribution and then a Landau-Liftshitz lineshape to describe the nanoparticle resonances. The essential feature of this model is that small particles have narrow linewidths and account for the g % 2 feature with a constant resonance field, whereas larger particles have broad linewidths and undergo a shift in resonance field. The second model assumes uniform particles with a diameter around 4 nm and a random distribution of uniaxial anisotropy axes. This model uses a more precise calculation of the linewidth due to superparamagnetic fluctuations and a random distribution of anisotropies. Sharp features in the spectrum near g % 2 are qualitatively predicted at high temperatures. Both models can account for many features of the observed spectra, although each has deficiencies. The first model leads to a nonphysical increase in magnetic moment as the temperature is increased if a log normal distribution of particles sizes is used. Introducing a bi-modal distribution of particle sizes resolves the unphysical increase in moment with temperature. The second model predicts low-temperature spectra that differ significantly from the observed spectra. The anisotropy energy density K 1 , determined by fitting the temperature-dependent linewidths, was $50 kJ/m 3 , which is considerably larger than that of bulk maghemite. The work presented here indicates that the magnetic properties of these size-constrained nanoparticles and more generally metal oxide nanoparticles with diameters d < 5 nm are complex and that currently existing models are not sufficient for determining their magnetic resonance signatures. V C 2012 American Institute of Physics. [http://dx

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Section: Discussionmentioning

confidence: 99%

Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

Usselman

Russek

Klem

et al. 2012

Journal of Applied Physics

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“…It is interesting to recall that the magnetization dynamics of nano scale antiferromagnets is a heavily debated topic in literature 33 . For such systems, measuring The TRM measurements (as a function of time 't' or temperature 'T') can reveal subtle magnetic features, which are not clearly visible in routine in-field magnetization measurements 33,35 .…”

Section: Figure 6 (A)-(d) Schematic Of Cr 2 O 3 Filled Cnt (Side and mentioning

confidence: 99%

A carbon-nanotube based nano-furnace for in-situ restructuring of a magnetoelectric oxide

Bajpai

Aslam

Hampel

et al. 2017

Carbon

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“…Mørup and Frandsen Reply: In their Comment [1], MacDonald and Canali claim that the magnetization of nanoparticles of antiferromagnetic materials cannot increase with increasing temperature as described in our Letter [2]. They argue that there are two equivalent degenerate spin-precession modes in an antiferromagnet with opposite magnetic moments, and the net magnetic moment therefore is zero.…”

mentioning

confidence: 99%

“…As we have pointed out [2], the average value of the thermoinduced magnetic moment of an antiferromagnetic particle is zero in the absence of an applied magnetic field. However, MacDonald and Canali seem to have failed to notice that Eq.…”

Thermoinduced Magnetization in Nanoparticles of Antiferromagnetic Materials

Cited by 107 publications

References 30 publications

Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

Temperature dependence of electron magnetic resonance spectra of iron oxide nanoparticles mineralized in Listeria innocua protein cages

A carbon-nanotube based nano-furnace for in-situ restructuring of a magnetoelectric oxide

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