Muons and magnets: publications

Relaxation of muon spins in molecular nanomagnets

Physical Review B - Condensed Matter and Materials Physics 81:14 (2010)

Authors:

T Lancaster, SJ Blundell, FL Pratt, I Franke, AJ Steele, PJ Baker, Z Salman, C Baines, I Watanabe, S Carretta, GA Timco, REP Winpenny

Abstract:

We address the cause of the unusual muon spin-relaxation (μ+ SR) results on molecular nanomagnets (MNMs). Through measurements on protonated and deuterated samples of the MNMs Cr7 Mn (S=1) and Cr8 (S=0), we show that the muon spin for S≠0 MNMs is relaxed via dynamic fluctuations of the electronic spins. A freezing out of dynamic processes occurs on cooling and at low temperatures the muon spins are relaxed by the electronic spins which themselves are dephased by incoherent nuclear-field fluctuations. We observe a transition to a state of static magnetic order of the MNM electronic spins in Cr7Mn below 2 K. © 2010 The American Physical Society.

The statistical mechanics of community assembly and species distribution

(2010)

Authors:

Colleen K Kellya, Stephen J Blundell, Michael G Bowler, Gordon A Fox, Paul H Harvey, Mark R Lomas, F Ian Woodward

Phase transition in the localized ferromagnet EuO probed by μsR

Physical Review B Condensed Matter and Materials Physics 81:9 (2010)

Authors:

SJ Blundell, T Lancaster, FL Pratt, PJ Baker, W Hayes, JP Ansermet, A Comment

Abstract:

We report results of muon-spin-rotation measurements performed on the ferromagnetic semiconductor EuO, which is one of the best approximations to a localized ferromagnet. We argue that implanted muons are sensitive to the internal field primarily through a combination of hyperfine and Lorentz fields. The temperature dependences of the internal field and the relaxation rate have been measured and are compared with previous theoretical predictions. © 2010 The American Physical Society.

Muon-spin relaxation and heat capacity measurements on the magnetoelectric and multiferroic pyroxenes LiFeSi2O6 and NaFeSi2O6

(2010)

Authors:

PJ Baker, HJ Lewtas, SJ Blundell, T Lancaster, I Franke, W Hayes, FL Pratt, L Bohaty, P Becker

Control of the competition between a magnetic phase and a superconducting phase in cobalt-doped and nickel-doped NaFeAs using electron count

Physical Review Letters 104:5 (2010)

Authors:

DR Parker, MJP Smith, T Lancaster, AJ Steele, I Franke, PJ Baker, FL Pratt, MJ Pitcher, SJ Blundell, SJ Clarke

Abstract:

Using a combination of neutron, muon, and synchrotron techniques we show how the magnetic state in NaFeAs can be tuned into superconductivity by replacing Fe by either Co or Ni. The electron count is the dominant factor, since Ni doping has double the effect of Co doping for the same doping level. We follow the structural, magnetic, and superconducting properties as a function of doping to show how the superconducting state evolves, concluding that the addition of 0.1 electrons per Fe atom is sufficient to traverse the superconducting domain, and that magnetic order coexists with superconductivity at doping levels less than 0.025 electrons per Fe atom. © 2010 The American Physical Society.

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