Probing magnetic order in heavily doped La2-xSrxNiO4+δ with μSR

We report μSR measurements on a series of compounds with composition La2-xSrxNiO4+δ where the net hole concentration x + 2δ is greater than 0.4. A magnetic transition is found in all the samples studied which occurs at a composition-dependent temperature TM. Below TM, clear precession signals are observed in zero applied magnetic field. The possible muon sites are discussed within the context of dipole-field calculations

Muon-spin-relaxation studies of magnetic order in heavily doped La2-xSrxNiO4+δ

We report muon-spin-relaxation measurements on a series of compounds with composition La2-xSrxNiO4+δ where the net hole concentration x+2δ is greater than 0.4. A magnetic transition is found in all the samples studied which occurs at a composition-dependent temperature TM. Below TM clear precession signals are observed in zero applied magnetic field, indicating the existence of at least short-range magnetic order on a time scale greater than 10-8 s. Above TM the correlation times decrease by several orders of magnitude. The measurements of TM as a function of the net hole concentration extend the determination of Néel temperatures by previous neutron diffraction measurements to higher doping levels

Deficits in social behavioral tests in a mouse model of alternating hemiplegia of childhood

Social behavioral deficits have been observed in patients diagnosed with alternating hemiplegia of childhood (AHC), rapid-onset dystonia-parkinsonism and CAPOS syndrome, in which specific missense mutations in ATP1A3, encoding the Na+, K+-ATPase α3 subunit, have been identified. To test the hypothesis that social behavioral deficits represent part of the phenotype of Na+, K+-ATPase α3 mutations, we assessed the social behavior of the Myshkin mouse model of AHC, which has an I810N mutation identical to that found in an AHC patient with co-morbid autism. Myshkin mice displayed deficits in three tests of social behavior: nest building, pup retrieval and the three-chamber social approach test. Chronic treatment with the mood stabilizer lithium enhanced nest building in wild-type but not Myshkin mice. In light of previous studies revealing a broad profile of neurobehavioral deficits in the Myshkin model – consistent with the complex clinical profile of AHC – our results suggest that Na+, K+-ATPase α3 dysfunction has a deleterious, but nonspecific, effect on social behavior. By better defining the behavioral profile of Myshkin mice, we identify additional ATP1A3-related symptoms for which the Myshkin model could be used as a tool to advance understanding of the underlying neural mechanisms and develop novel therapeutic strategies