Coexistence of Universal and Topological Anomalous Hall Effects in Metal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>CrO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>Thin Films in the Dirty Limit

Branford, W. R.; Yates, K. A.; Barkhoudarov, E.; Moore, J D; Morrison, Kelly; Magnus, Fridrik; Miyoshi, Yasuyuki; Sousa, Paulo; Conde, O.; Silvestre, A. J.; Cohen, L. F.

doi:10.1103/physrevlett.102.227201

Cited by 20 publications

(12 citation statements)

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“…A strong correlation between the spins of localized and nonlocalized electrons makes the Hall effect and also the anomalous Hall effect a subtle tool to probe topological spin defects of the 3D ferromagnetic material. 13,14 The compound CrO 2 is a metastable phase and bulk material is synthesized at high pressures. Deposition techniques such as sputtering, pulsed laser deposition, or molecular beam epitaxy cannot be used, but high-quality thin films can be grown using the technique of chemical vapor deposition (CVD) at ambient pressure, as for instance discussed in Refs.…”

Section: Materials and Sample Preparationmentioning

confidence: 99%

“…Watts et al presented data showing a sign reversal at low temperatures, 12 which they interpreted as evidence for two-band transport, but this was not found in later studies. 13,14 In this article we return to the issue of magnetotransport in high-quality thin films of CrO 2 , with proper attention to the different crystallographic axes of the material. We find resistivity behavior that is subtly different from earlier reports, with an anomaly around 100 K. We do not see a sign change in the Hall effect reported in Ref.…”

Section: Introductionmentioning

confidence: 99%

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Anomalous transport in half-metallic ferromagnetic CrO2

Anwar

Aarts

2013

Phys. Rev. B

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We have investigated the transport properties of CrO 2 thin films deposited on TiO 2 and sapphire substrates and find subtle differences with respect to earlier reports. The films are good metals down to low temperatures, with residual resistivities of the order of 6 μ cm for films deposited on TiO 2 and two times higher for films on sapphire substrates. Magnetoresistance (MR) measurements in high fields show an as yet unobserved nonmonotonic behavior, which is particularly pronounced around the sign change that takes place from negative to positive at a temperature around 100 K. Moreover, both the ordinary and anomalous Hall coefficients show considerable changes around 100-150 K, suggesting a change in carrier density together with the onset of the influence of spin defects in this temperature window. At lower temperatures, the MR is a linear function of the applied field, which can be explained as intergrain tunneling MR. This interpretation is also suggested by the angular MR. Planar Hall effect measurements reveal that the CrO 2 thin films are not in a single magnetic domain state even for films deposited on an isostructural TiO 2 substrate.

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Section: Materials and Sample Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anomalous transport in half-metallic ferromagnetic CrO2

Anwar

Aarts

2013

Phys. Rev. B

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“…Gupta et al 13 fit the low-temperature resistivity (below 40 K) with a ρ(T ) = ρ 0 + AT 3 dependence characteristic of spin-flip scattering if the non-rigid band behavior of the minority band is accounted for. Watts et al proposed a two-band picture for electronic conduction based on a magnetotransport study 14 , although other magnetoresistance studies have not reached the same conclusion 15,16 . Several authors found that a T 2 dependence also describes well the resistivity data in a broad temperature range and attributed this to electron-electron scattering 9,17 .…”

Section: Introductionmentioning

confidence: 99%

Role of spin fluctuations in the conductivity ofCrO2

et al. 2016

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We present a time-resolved terahertz spectroscopic study of the half-metallic ferromagnet CrO 2 .The ultrafast conductivity dynamics excited by an optical pump displays a very short (several picoseconds) and a very long (several hundred picoseconds) characteristic time scales. We attribute the former to the electron-phonon relaxation and the latter to the spin-lattice relaxation. We use this distinction to quantify the relative contribution of the scattering by spin fluctuations to the resistivity of CrO 2 : we find that they contribute less than one half of all scattering events below room temperature. This contribution rises to ∼ 70% as the temperature approaches T C =390 K.The small effect of spin fluctuations on the resistivity is unexpected in the light of the proposed double-exchange nature of the electronic and magnetic properties of CrO 2 .

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“…This mechanism produces an anomalous Hall signal called the topological Hall effect (14)(15)(16)(17).…”

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Emerging Chirality in Artificial Spin Ice

Branford

Ladak

Read

et al. 2012

Science

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123

142

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Artificial spin ice, made up of planar nanostructured arrays of simple ferromagnetic bars, is a playground for rich physics associated with the spin alignment of the bars and spin texture associated with the magnetic frustration at the bar vertices. The phase diagram is exotic, showing magnetic monopole-like defects and liquid and solid phases of spins arranged in loop states with predicted chiral order. We show that magnetotransport measurements in connected honeycomb structures yield the onset of an anomalous Hall signal at 50K. The temperature scale can be attributed to the long-range dipolar ice phase.The topological Hall signal arises because chiral loops form at the sample edges, indicating a generic route to exotic states via nanoarray edge structure.

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Coexistence of Universal and Topological Anomalous Hall Effects in MetalCrO2Thin Films in the Dirty Limit

Cited by 20 publications

References 22 publications

Anomalous transport in half-metallic ferromagnetic CrO2

Anomalous transport in half-metallic ferromagnetic CrO2

Role of spin fluctuations in the conductivity ofCrO2

Emerging Chirality in Artificial Spin Ice

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