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Showing content from https://pubmed.ncbi.nlm.nih.gov/27882917 below:

Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3

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doi: 10.1038/ncomms13406. Optically switched magnetism in photovoltaic perovskite CH₃NH₃(Mn:Pb)I₃

Affiliations

¹ Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
² Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
³ Swiss-Norwegian Beam Lines, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, F-38043 Grenoble Cedex 9, France.
⁴ DQMP-University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.

PMID: 27882917
PMCID: PMC5123013
DOI: 10.1038/ncomms13406

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Optically switched magnetism in photovoltaic perovskite CH₃NH₃(Mn:Pb)I₃

B Náfrádi et al. Nat Commun. 2016.

doi: 10.1038/ncomms13406. Affiliations

¹ Laboratory of Physics of Complex Matter, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
² Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
³ Swiss-Norwegian Beam Lines, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, F-38043 Grenoble Cedex 9, France.
⁴ DQMP-University of Geneva, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.

PMID: 27882917
PMCID: PMC5123013
DOI: 10.1038/ncomms13406

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Abstract

The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH₃NH₃(Mn:Pb)I₃ material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman-Kittel-Kasuya-Yosida interactions without heating up the spin system. Our finding offers an alternative, very simple and efficient way of optical spin control, and opens an avenue for applications in low-power, light controlling magnetic devices.

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Figures
Figure 1. Sample and measurement configuration.

(…

Figure 1. Sample and measurement configuration.

( a ) Photo of a typical CH _3…

Figure 1. Sample and measurement configuration.

(a) Photo of a typical CH₃NH₃(Mn:Pb)I₃ crystal, 10–15 were assembled for the ESR measurement. (b) Sketch of the crystal structure of CH₃NH₃(Mn:Pb)I₃. (c) The experimental configuration for the high-field ESR measurements showing the assembly of small crystals (sample). The absorption of the microwave field provided by the microwave source (MW source, up to 315 GHz) is monitored (MW detector) in resonant conditions in dark and under illumination in reflection geometry (MW mirror). The light source is a red (λ=655 nm, 4 μW cm⁻²) LED activated by an external switch (switch).

Figure 2. Magnetic properties of CH _3…

Figure 2. Magnetic properties of CH ₃ NH ₃ (Mn:Pb)I ₃ in dark.

( a ) ESR linewidth (red dots)…

Figure 2. Magnetic properties of CH₃NH₃(Mn:Pb)I₃ in dark.

(a) ESR linewidth (red dots) and resonant field (blue dots, offset by a reference value B₀) as a function of temperature recorded at 9.4 GHz. Their temperature-independent behaviour is characteristic for the paramagnetic phase (PM). The upturn below 25 K corresponds to the on-set of the FM phase. Inset: SQUID magnetometry of MAMn:PbI₃. The temperature dependence of the spontaneous magnetization measured in 1.2 μT magnetic field shows a clear increase below T_C. The red line represents the M₀(1−(T/T_C)^3/2) temperature dependence given by Bloch's Law. (b) First-principles calculations of the atomic configurations and magnetic order show total density of states (DOS) and projected density of states (PDOS) calculated for the in-plane model of CH₃NH₃(Mn:Pb)I₃ in its neutral FM configuration. (c) Calculated Pb–I and Mn–I distances for a single Mn dopant. (d) Calculated bond angles and bond distances for the I mediated super-exchange paths in the FM ground state of the in-plane model of CH₃NH₃(Mn:Pb)I₃.

Figure 3. Illumination effect on the magnetic…

Figure 3. Illumination effect on the magnetic properties of CH ₃ NH ₃ (Mn:Pb)I _3…

( a…

Figure 3. Illumination effect on the magnetic properties of CH₃NH₃(Mn:Pb)I₃ measured by ESR.

(a) The intensity change as the function of the illuminating red light intensity Φ at T=5 K. Above a threshold value, the FM part of the signal decreases monotonously. (b) Light-on ESR linewidth normalized to the linewidth in dark. The narrowing of the linewidth on illumination starts below T_C. (c) ESR spectra at 157 GHz and 5 K of pristine CH₃NH₃PbI₃ (green line–no signal), of CH₃NH₃(Mn:Pb)I₃ in dark (blue line) coming from the FM phase and its reduction (red line) on visible light illumination. The difference between light-off and light-on ESR signals is shown in orange. The effect is accompanied by narrowing of the ESR linewidth on illumination. (d) Difference of the ESR intensities between the light-off and light-on measurements as a function of temperature. (The third axis shows the resonant field of the signal.) The intensity reduction on illumination is present only below T_C=25 K, in the FM phase. Error bars represent the confidence interval of least square fits to the spectra.

Figure 4. Schematic illustration of writing a…

Figure 4. Schematic illustration of writing a magnetic bit.

In the dark ( a )…

Figure 4. Schematic illustration of writing a magnetic bit.

In the dark (a) the spin alignment corresponds to a given orientation of the magnetic moment in the FM state, representing a bit. On illumination (b) the FM order melts and a small magnetic field of the writing head will set the orientation of the magnetic moment once the light is switched off (c).