Chapter 2 Magnetic materials studied by muon spin rotation spectroscopy

Schenck, A.; Gygax, F. N.

doi:10.1016/s1567-2719(05)80006-x

Cited by 80 publications

(105 citation statements)

References 499 publications

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“…1. The fact that the depolarization due to the samples is well described by the Kubo-Toyabe function is a strong indication that the spins of the muons are depolarized by a static field distribution [13,14]. This interpretation is confirmed by additional measurements performed at high and low temperatures with a magnetic field of 10 mT applied along the Z axis : with this experimental set-up the spectra are not depolarized.…”

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confidence: 62%

“…The decay positron 1 is emitted preferentially along the final muon spin direction; by collecting several million positrons, we can reconstruct the time dependence of the muon spin depolarization function P Z (t) which, in turn, reflects the distribution of fields experienced at the muon site. The Z axis refers to the muon beam polarization axis which, in our case, is as well the direction of the detected positrons because the measurements have been performed with the longitudinal geometry [13,14]. P Z (t) has been deduced from the raw data using the method described in Ref.…”

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confidence: 99%

“…In the µSR technique polarized muons are implanted into a sample where their spin evolves in the local magnetic field until they decay [13,14]. The decay positron 1 is emitted preferentially along the final muon spin direction; by collecting several million positrons, we can reconstruct the time dependence of the muon spin depolarization function P Z (t) which, in turn, reflects the distribution of fields experienced at the muon site.…”

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confidence: 99%

“…Therefore the observed depolarization is induced by the nuclear magnetic moments which are almost uniquely carried by the 195 Pt nuclei of abundance 33.7 %. Given a muon localization site, ∆ 2 KT due to nuclear moments can be computed using the well known formula [13,14] …”

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Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

et al. 1995

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We present muon spin relaxation measurements performed on crystals of the heavy fermion superconductor UPt3. In zero applied field, contrary to a previous report, we do not observe an increase of the internal magnetic field in the lower superconducting phase (the B phase). Our result gives an experimental upper bound of the magnetic field that could be associated with the superconducting state.PACS numbers : 74.70. Tx, 75.20.Hr, 76.75.+i The unconventional nature of superconductivity in the hexagonal heavy fermion superconductor UPt 3 is now well established [1]. This was first convincingly demonstrated by the occurence in zero magnetic field of two superconducting phase transitions at T C+ ≃ 0.50 K and T C * ≃ 0.45 K. Despite intense experimental and theoretical activities, the nature of superconductivity in UPt 3 is still unknown. Even the question of the symmetry of the superconducting order parameter is not resolved [2,3].Recently Luke et al. have reported zero field muon spin relaxation (µSR) measurements which show that the relaxation rate increases when crossing T C * from above [4,5]. This observation has been taken as a proof that the B phase (the low temperature superconducting phase below T C * ) breaks time reversal symmetry and is characterized by triplet Cooper pairs. This remarkable result has attracted much interest [6,7,2,8,3].The physical properties of heavy fermion metals are well known to be extremely dependent on the sample quality. High quality crystals are now available. These two facts have been our original motivation for performing new µSR measurements, the results of which are presented in this letter.The samples were prepared from two large single crystals of UPt 3 grown by the Czochralski method under ultrahigh vacuum from zone-refined depleted uranium. The as-grown crystals were annealed for several days at 1200 • C -1300 • C (see Ref.[9]), and then spark-cut or wire-sawed. The cut plates were annealed for an additional week at 950 • C, improving the sharpness of the resistivity transition (an example is presented at Fig. 1 of Ref. [10]). The resistivity of our samples, measured on long samples (8 mm length, 0.3 × 0.4 mm 2 cross section) obeys ρ(T ) = ρ(0) + AT 2 perfectly below 1.1 K, with ρ c (0) = 0.28 µΩcm, ρ a (0) = 0.51 µΩcm and A c = 0.90 µΩcmK −2 , A a = 1.46 µΩcmK −2 for current parallel to c and a. These low residual resistivities, which are comparable with recently published values [11], are a proof of the high quality of our samples.The µSR measurements were carried out on two samples which differ by the orientation of the crystal axes relative to the sample plane : either c or a * (≡ b) is perpendicular to it. Each sample is a disk of ∼ 18 mm diameter and ∼ 0.4 mm thickness, comprising of a mosaic of ∼ 10 aligned slices of the same single crystal carefully glued to a 5N silver plate (40 × 40 mm 2 ). To ensure good thermal contact at low temperature, each slice is ultrasonically bonded to a gold wire clamped to the silver plate. This method allows to reach low tempera...

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Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

et al. 1995

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“…[1][2][3] Spin polarized positive muons with an energy of ≈4 MeV are implanted into a sample. The muons decay with a mean lifetime of ≈2.2 μs and emit a positron preferentially in the direction of their spin at the instant of decay.…”

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Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

Lord

McKenzie

Baker

et al. 2011

Review of Scientific Instruments

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. The high magnetic field (HiFi) muon instrument at the ISIS pulsed neutron and muon source is a state-of-the-art spectrometer designed to provide applied magnetic fields up to 5 T for muon studies of condensed matter and molecular systems. The spectrometer is optimised for time-differential muon spin relaxation studies at a pulsed muon source. We describe the challenges involved in its design and construction, detailing, in particular, the magnet and detector performance. Commissioning experiments have been conducted and the results are presented to demonstrate the scientific capabilities of the new instrument.

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Hyperfine Interactions

2007

Mössbauer Effect in Lattice Dynamics

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In a system where magnetic ions occupy the vertices of edge or corner sharing triangular units, the natural antiferromagnetic coupling between ions is geometrically frustrated. A wide variety of interesting magnetic behaviour has been observed in pyrochlores, where magnetic ions form a network of corner sharing tetrahedra. The low temperature spin dynamics of a number of pyrochlores A2B2O7 have been investigated using the technique of µSR. For example, Y2Mo2O7 shows a transition to a disordered magnetic state similar to a spin glass at TF = 22 K. However, unlike conventional metallic spin glasses, a non-zero muon spin depolarization rate is observed to persist well below 0.1 TF. These results suggest that there is a finite density of states for magnetic excitations in this system near zero energy.Recently, there has been a considerable interest in the behaviour of systems where the natural antiferromagnetic coupling between ions is frustrated by the geometry of the lattice. In three dimensions, the most well studied systems have a pyrochlore structure. Frustrated systems are characterized by a suppression of the ordering temperature T c relative to the Curie-Weiss temperature, θ. Within the mean field theory, T c is given by T c = 2 3 zS(S + 1)k B |J| for both ferromagnets and two sublattice antiferromagnets, where z is the number of nearest neighbours, S the spin and J is the exchange interaction. In a ferromagnetic or unfrustrated antiferromagnetic system, the high temperature susceptibility is then χ = µ 2 B g 2 S(S + 1) 3k B (T − θ) ,© J.C. Baltzer AG, Science Publishers

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Chapter 2 Magnetic materials studied by muon spin rotation spectroscopy

Cited by 80 publications

References 499 publications

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Absence of zero field muon spin relaxation induced by superconductivity in the B phase of UPt3

Design and commissioning of a high magnetic field muon spin relaxation spectrometer at the ISIS pulsed neutron and muon source

Hyperfine Interactions

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