20 research outputs found
The magnetic structure of the chain family NaCaVO determined by muon-spin rotation
We present muon-spin rotation measurements on polycrystalline samples of the
complete family of the antiferromagnetic (AF) chain compounds,
NaCaVO. In this family, we explore the magnetic properties
from the metallic NaVO to the insulating CaVO. We find a
critical which separates the low and high Na-concentration
dependent transition temperature and its magnetic ground state. In the
compounds, the magnetic ordered phase is characterized by a single homogenous
phase and the formation of incommensurate spin-density-wave order. Whereas in
the compounds, multiple sub-phases appear with temperature and .
Based on the muon data obtained in zero external magnetic field, a careful
dipolar field simulation was able to reproduce the muon behavior and indicates
a modulated helical incommensurate spin structure of the metallic AF phase. The
incommensurate modulation period obtained by the simulation agrees with that
determined by neutron diffraction.Comment: 7 pages, 7 figures, accepted for publication in PR
The magnetic phase of the perovskite CaCrO studied with SR
We investigated the magnetic phase of the perovskite CaCrO by using the
muon spin relaxation technique accompanied by susceptibility measurements. A
thermal hysteresis loop is identified with a width of about 1 K at the
transition temperature. Within the time scale of the muon lifetime, a static
antiferromagnetic order is revealed with distinct multiple internal fields
which are experienced in the muon interstitial sites below the phase-transition
temperature, . Above , lattice deformations are indicated by
transverse-field muon-spin rotation and relaxation suggesting a magneto-elastic
mechanism.Comment: 5 pages, 4 figures. Accepted for publication in PR
The Magnetic Phase of Lithium Transition Metal Phosphates LiMPO4 (M=Mn, Co, Ni) Detected by μ+SR
AbstractThe magnetic properties of the olivine-type compounds LiMPO4 (M = Mn, Co, Ni) are probed using muon spin rotation/relaxation (μSR). These materials pose an appealing magnetic structure and a high -potential technological interest as cathode materials for future rechargeable Li-ion batteries. The LiMPO4 family of compounds consists of a corner-sharing MO6 octahedra of high-spin M2+ ions manifesting an antiferromagnetic ground state below TN ≈ 30K. Additionally, these compounds belong to a class of materials exhibiting properties between two-and three dimensional systems. A comparative study between the family members is presented
Static magnetic order in NaCoO detected by muon spin rotation and relaxation
The nature of the magnetic transition of the Na-rich thermoelectric
NaCoO at 22K was studied by positive muon-spin-rotation and
relaxation (SR) spectroscopy, using a polycrystalline sample in the
temperature range between 300 and 2.5 K. Zero field SR measurements
indicated the existence of a static internal magnetic field at temperatures
below 22 K (= ). The observed muon spin precession signal below
consisted of three components with different precession
frequencies, corresponding to three inequivalent muon sites in the
NaCoO lattice. The total volume fraction of the three components
was estimated as 21% at 2.5 K; thus, this magnetic transition was not
induced by impurities but is an intrinsic change in the magnetism of the
sample, although the sample was magnetically inhomogeneous otherwise. On the
other hand, a similar experiment on a NaCoO sample exhibited no
magnetic transition down to 2.5 K; which indicates that the average valence of
the Co ions is responsible for inducing the magnetic transition at 22 K.Comment: 5 pages, 4 figures, Phys. Rev. B 68 (2003) in pres
Frustration and magnetism of the zigzag chain compounds EuL2O4 (L = Yb, Lu, Gd, Eu)
We present muon-spin rotation/relaxation and susceptibility measurements on polycrystalline samples of EuL2O4, where L is the lanthanide Yb, Lu, Gd, or Eu. The magnetic phase of these quasi-one-dimensional zigzag chain compounds is characterized with respect to the difference in their lanthanide magnetic moment. We find that the magnetic phase varies systematically with the lanthanide magnetic moment. At zero lanthanide moments (EuLu2O4), we find a static antiferromagnetic phase; as the moment increases, the phase gradually changes to an incommensurate spin-density-wave ordered phase, and finally reaches a dynamic phase, when large lanthanide magnetic moments are present (EuGd2O4)
The gradient distribution of Ni ions in cation-disordered Li[Ni1/2Mn3/2]O-4 clarified by muon-spin rotation and relaxation (mu SR)
Cation-ordered Li[Ni1/2Mn3/2]O-4 with a P4(3)32 space group (CO-LNMO) and "cation-disordered'' (CDO) LNMO are thought to be the state-of-the-art materials for lithium-ion batteries. However, in contrast to CO-LNMO, the crystal structure and electrochemical reaction scheme of CDO-LNMO are not fully understood. We have measured the muon-spin rotation and relaxation (mu SR) spectra for samples of both CO-LNMO and CDO-LNMO, in particular at their magnetic transition temperatures (T-C) below 130 K. The weak transverse field (wTF) mu SR measurements reveal that the range of T-C for the CDO-LNMO sample is very large (Delta T-C similar to 55 K) compared with that for the CO-LNMO sample (Delta T-C < 5 K). This suggests an inhomogeneous cation distribution in the CDO-LNMO sample, because the sample consists of multiple phases with different T-C. Based on the wTF-mu SR result for stoichiometric LiMn2O4, we have proposed that CDO-LNMO is a mixture of L[Ni1/2-omega Mn3/2+omega]O-4 and LiMn2O4