μSR study of stoichiometric NbFe2

Abstract

The magnetic ground state of nominally stoichiometric single crystalline NbFe 2 is investigated by bulk magnetisation and muon spin relaxation techniques. Magnetic order clearly emerges below the critical temperature T N =10.3 K and is dominated by randomly orientated quasi-static moments. The local field distribution observed by muons can be explained by the phenomenological Gaussian-broadened-Gaussian Kubo Toyabe relaxation function. The observed short range order could be used to describe a new magnetic ground state, but a helical spin density wave with an incommensurate amplitude modulation cannot be ruled out. The sensitivity of µSR to the local magnetic field distribution in the vicinity of the quantum critical point (QCP) in NbFe 2 is clearly demonstrated via comparison with already published work. This suggests detailed measurements of the muon relaxation as the QCP is approached will reveal further details of the field distribution and fluctuations in Nb 1−y Fe 2+y .

Muon spin rotation and relaxation study on Nb$_{1-y}$Fe$_{2+y}$

“…Conversely, in a paramagnetic phase at both muon sites there will be essentially the same field and field distribution, and the assumption of a single muon stopping will be sufficient to fit the experimental data (the site occupation in the SDW phase will be discussed in the following subsection). This conclusion is in full accordance with the fit procedures used in previous µSR studies on Nb 1−y Fe 2+y 19,20 .…”

“…By now, these findings have been validated by a multitude of experimental techniques including microscopic probes such as muon spin relaxation and elastic neutron scattering. [19][20][21] . It was concluded, that the ferromagnetic phases have a magnetic moment below 0.1 µ B /Fe atom 17,19,21 .…”

“…Therefore, here, we present detailed muon spin relaxation (µSR) measurements on a polycrystalline sample Nb 1.0117 Fe 1.9883 , for which thermodynamic studies have neither found evidence for a SDW nor a ferromagnetic transition 24 . Regarding µSR studies, it was previously assumed that there are two distinct muon stopping sites in NbFe 2 19,20 . In order to verify this statement and to allow a full quantitative analysis of the µSR-spectra, we have determined the muon positions on a Nb 0.982 Fe 2.018 single crystal.…”

Muon spin rotation and relaxation study on Nb1−yFe2+y

“…The magnetic phases of Nb 1−y Fe 2+y at low temperatures exhibit a strong sensitivity on the actual sample composition, resulting in a complex magnetic phase diagram [13][14][15][16]. Extensive investigations in recent years using different measurement techniques have established that Nb 1−y Fe 2+y can be pushed into a quantum critical point (QCP) by variation of y [16][17][18][19][20][21][22], with the phase diagram depicted in Fig. 1.…”

“…By now, these findings have been validated by a multitude of experimental techniques including microscopic probes such as muon spin relaxation and elastic neutron scattering. [19][20][21]. It was concluded that the ferromagnetic phases have a magnetic moment below 0.1 μ B /Fe atom [17,19,21].…”