Generation and applications of slow polarized muons

Bakule, Pavel; Morenzoni, E.

doi:10.1080/00107510410001676803

Cited by 85 publications

(75 citation statements)

References 47 publications

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“…For this, we used the technique of low-energy muon spin rotation 16,17 (LE-μSR), which has previously been applied successfully to obtain the depth-resolved profile of the local magnetization in various thin films and heterostructures 18,19 . The stopping distribution of the fully spin-polarized muons can be varied here on the scale of about 3-200 nm through the control of the muon implantation energy.…”

Section: Measurement Of Spin Penetrationmentioning

confidence: 99%

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

et al. 2008

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Electronic devices that use the spin degree of freedom hold unique prospects for future technology. The performance of these 'spintronic' devices relies heavily on the efficient transfer of spin polarization across different layers and interfaces. This complex transfer process depends on individual material properties and also, most importantly, on the structural and electronic properties of the interfaces between the different materials and defects that are common to real devices. Knowledge of these factors is especially important for the relatively new field of organic spintronics, where there is a severe lack of suitable experimental techniques that can yield depth-resolved information about the spin polarization of charge carriers within buried layers of real devices. Here, we present a new depth-resolved technique for measuring the spin polarization of current-injected electrons in an organic spin valve and find the temperature dependence of the measured spin diffusion length is correlated with the device magnetoresistance.R ecently great efforts have been undertaken to use the spin degree of freedom in electronic devices. These activities are fuelled by the potential prospects of spin-electronic (or 'spintronic') devices for example in terms of increased processing speed and integration, non-volatility, reduced power consumption, multifunctionality and their suitability for quantum computing 1 . The most common method for using the spin in devices is based on the alignment of the electron spin ('up' or 'down') relative to either a reference magnetic field or the magnetization orientation of a ferromagnetic layer. Device operation normally proceeds with measuring a quantity such as the electrical current that depends on how the degree of spin alignment is transferred across the device. The so-called 'spin valve' is a prominent example of such a spin-enabled device that has already revolutionized hard-drive read heads and magnetic memory 1 . The efficient transfer of spin polarization in real device structures remains one of the most difficult challenges in spintronics, because it is dependent on more than just the properties of the individual materials that comprise the device.Recently 2,3 , the use of organic materials in spintronics has become of significant interest, primarily owing to their ease and small cost of processing and electronic and structural flexibility. Furthermore, the extremely long spin coherence times found in organic materials offer considerable advantages over other materials 3 . This favourable property is related to two factors, first the weak spin-orbit coupling of light elements such as carbon and second to the small nuclear hyperfine interaction 4,5 . The latter arises because the electron transport in π-conjugated molecules is normally confined to molecular states, delocalized to the carbon rings, the predominant isotope of which, 12 C, has zero nuclear spin 4 .A common way to measure spin diffusion is based on time-resolved optical techniques, where spin-polarized charge carrie...

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Section: Measurement Of Spin Penetrationmentioning

confidence: 99%

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

et al. 2008

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“…It has been shown that with the formation of the metastable magnetic centers, the material becomes less absorbing in the wavelength region relevant to the photomagnetism [32], thus it is possible that the photomagnetic state would eventually grow out from the illuminated surfaces, but such an effect was apparently not sufficient to influence the magnetism on the ∼ 100 µm surface muon stopping range. A more favorable situation to study these effects is in a thin film geometry [33] using low energy muons [34] or β-NMR probes [35,36,37].…”

Section: F Sample Illuminationmentioning

confidence: 99%

Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets

et al. 2006

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We present longitudinal field muon spin relaxation (µSR) measurements in the unilluminated state of the photo-sensitive molecular magnetic Co-Fe Prussian blue analogues M1−2xCo1+x[Fe(CN)6]·zH2O, where M=K and Rb with x = 0.4 and ≃ 0.17, respectively. These results are compared to those obtained in the x = 0.5 stoichiometric limit, Co1.5[Fe(CN)6]·6 H2O, which is not photo-sensitive. We find evidence for correlation between the range of magnetic ordering and the value of x in the unilluminated state which can be explained using a site percolation model. A. IntroductionPrussian Blue (PB) (Fe 4 [Fe(CN) 6 ] 3 ) is a long-known dye and prototypical transition metal co-ordination compound that exhibits ferro-magnetism [1,2,3] driven by superexchange coupling between iron spins. It is an important case of exchange coupling mediated through the CN − bridge [4]. Much of the recent interest in magnetic compounds related to PB (including a few that have been studied with µSR [5,6,7]) is motivated by potential novel behavior and related applications in molecular magnetism [8,9], including magnetism that is sensitive to exposure to light, i.e. photomagnetism.The compounds studied in this paper are the molecule based Co-Fe PB analogues (Co-Fe PBAs)1: (Color online) Crystal structure of M1−2xCo1+x[Fe(CN)6]·zH2O: (a) x = 0.5; (b) x = 0.5, with an Fe(CN)6 vacancy shown in gray coordinated by bound water molecules. Large, medium and small circles denote Fe, Co, and CN, respectively. The alkali ions which maintain charge neutrality occupy cubic interstitial sites (not shown).1 This chemical formula is a commonly used approximation though [8,9,12]. These compounds have the sodium chloride structure, with Co and Fe ions located on the vertices of a cubic lattice, each octahedrally coordinated by six cyano moieties (Fig. 1). The Co and Fe ions are connected via cyanide bridges with interstitial alkali metal ions and water molecules [9,13] (Fig. 1(b)). Co-Fe PBAs are in general non-stoichiometric and significant structural disorder (vacancies in the Fe(CN) 6 sites) is present. Depending on the stoichiometry and synthesis route, the materials are paramagnets or exhibit magnetic ordering at temperatures below ∼ 25 K, due to small superexchange coupling J between Fe III and Co II moments.Illumination of Co-Fe PBAs with broadband visible light in the range of ∼ 550 − 750 nm can cause dramatic changes in the magnetic properties, including an increase in magnetization and ordering temperature. The proposed origin of the photomagnetic effect is a light-induced charge transfer from the state: Fe II (t 6 2g , S = 0)-CNCo III (t 6 2g , S = 0) to the meta-stable self-trapped state: Fe III (t 5 2g , S = 1/2)-CN-Co II (t 5 2g e 2 g , S = 3/2) [9,14], effectively increasing the concentration of magnetic moments. The non-stoichiometry is believed essential for the photoinduced magnetization [14]. However, in spite of considerable experimental and theoretical effort, the microscopic mechanism of the photomagnetic effect and the nature of magnetic orde...

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“…This allows the average probing depth to be tuned from about 10 to 100 nm below the surface. For a typical measurement several million counting events are collected at a rate of about 1k/s and errors as small as 0.1 G can be achieved [19] (see Suppl.…”

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confidence: 99%

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

et al. 2018

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We have observed the spatial distribution of magnetic flux in Nb, Cu/Nb and Cu/Nb/Co thin films using muon-spin rotation. In an isolated 50 nm thick Nb film we find a weak flux expulsion (Meissner effect) which becomes significantly enhanced when adding an adjacent 40 nm layer of Cu. The added Cu layer exhibits a Meissner effect (due to induced superconducting pairs) and is at least as effective as the Nb to expel flux. These results are confirmed by theoretical calculations using the quasiclassical Green's function formalism. An unexpected further significant enhancement of the flux expulsion is observed when adding a thin (2.4 nm) ferromagnetic Co layer to the bottom side of the Nb. This observed cooperation between superconductivity and ferromagnetism, by an unknown mechanism, forms a key ingredient for developing superconducting spintronics.

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Generation and applications of slow polarized muons

Cited by 85 publications

References 47 publications

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Direct measurement of the electronic spin diffusion length in a fully functional organic spin valve by low-energy muon spin rotation

Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets

Observation of Anomalous Meissner Screening in Cu/Nb and Cu/Nb/Co Thin Films

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