Muon-Probing sites and states in MgO and GdBCO

A computational model is used to locate the muon sites in MgO. The positive muon localizes in a vacant oxygen tetrahedron. This work supports μSR MgO [1] & MnO studies. For MnO, one μ⁺ signal is observed. [2] In MgO, an extra sharp signal has been seen, suggesting extended O[-1] states. [1] Shekhter et al [3] found, the μ⁺ reduces strongly cuprate loop currents. [4] Site-search calculations for RBa₂Cu₃O_7-δ (RBCO) [5] generated candidate Balmer (Bi) and Lin (Li) muon sites. These sites are ~1 Å away from O^2- ions in insulating regions. The B_i sites are near the BaO layer and are observed; [5] B2 is the favorite site. The L_i sites are near the CuO-chain layer and rarely cited. [4] Our ME-TF-μSR [6] GdBCO study confirms, muons probe away from the superconducting CuO₂ planes.
1] C Boekema et al, APS March meeting (2016). [2] YJ Uemura et al, Hpf Int 17-19 (1984) 339. [3] A Shekhter et al, Phys Rev Lett 101 (2008) 227004. [4] C Boekema et al, Physica C49 (2013) 136; T Songatikamas et al, J Supercond & Novel Magn 23 (2010) 793. [5] WK Dawson et al, J Appl Phys 64 (1988) 5809; Hpf Int 63 (1990) 219. [6] C Boekema & MC Browne, MaxEnt 2008, AIP Conf Proc #1073 p260.