Understanding theμSR spectra of MnSi without magnetic polarons

Abstract

Transverse-field muon-spin rotation (µSR) experiments were performed on a single crystal sample of the non-centrosymmetric system MnSi. The observed angular dependence of the muon precession frequencies matches perfectly the one of the Mn-dipolar fields acting on the muons stopping at a 4a position of the crystallographic structure. The data provide a precise determination of the magnetic dipolar tensor. In addition, we have calculated the shape of the field distribution expected below the magnetic transition temperature TC at the 4a muon-site when no external magnetic field is applied. We show that this field distribution is consistent with the one reported by zero-field µSR studies. Finally, we present ab initio calculations based on the density-functional theory which confirm the position of the muon stopping site inferred from transverse-field µSR. In view of the presented evidence we conclude that the µSR response of MnSi can be perfectly and fully understood without invoking a hypothetical magnetic polaron state.

Transverse field muon-spin rotation measurement of the topological anomaly in a thin film of MnSi

“…In fact, correcting the shift for the Lorentz field and the demagnetizing field gives the Knight shift shown in the inset in Fig. 3, which when plotted against χ ≈ μ 0 M/B, measured at B = 150 mT, allows us to estimate a contact hyperfine coupling of A HF = −0.95(5) mol emu −1 , consistent with previous measurements [29].…”

“…Helical and SL distributions are generated as described previously [28], while cone-phase distributions are generated using [21] m(r)/m 0 =x sin θ cos (q · r) +ŷ sin θ sin(q · r) +ẑ cos θ, where cos θ = |B|/B c2 and B ẑ [111]. The magnetic moment is taken to be 0.4μ B [32], B c2 = 0.5 T (corresponding to T film c ≈ 40 K [21]) and the length scale of the helical [29] and conical structures is taken to be 18 nm. For the skymion lattice we consider lattice constants suggested in previous studies of both L sk = 18 nm [12] and 8.5 nm [14], although there is little difference between the two.…”

“…For the skymion lattice we consider lattice constants suggested in previous studies of both L sk = 18 nm [12] and 8.5 nm [14], although there is little difference between the two. We evaluate dipole fields from the moment distributions along with the contribution from the contact hyperfine field, calculated using [29] is the hyperfine coupling from Ref. [29], and N is the number of Mn ions within one lattice constant of the muon site.…”

High-pressure magnetic state of MnP probed by means of muon-spin rotation

“…wide-gap semiconductors, insulating systems or cuprate and iron-based high-T c superconductors. [20][21][22][23][24][25] There are four equivalent minima in the unit cell corresponding to the 4c [(x, 1/4, z), x µ = 0.103, z µ = 0.921] Wyckoff position (see the Supplementary part). The calculations were started from the known FM and Hel−c magnetic structures at ambient pressure (see Refs.…”

Toward the Computational Prediction of Muon Sites and Interaction Parameters

“…For MnSi the site identification by DFT, supporting accurate transverse field experiments and a careful data analysis, proved that the observed frequencies correspond to the latter case. 37,38 A similar instance is that of deconfined magnetic monopoles that are predicted by theory in spin ices, such as in some rare earth pyrochlores. A recent experiment claimed to have detected by µSR in Dy 2 Ti 2 O 7 a second Wien effect, also referred to as magnetricity, i.e.…”