Figure 4

(a) \(\mu ^+\)SR time spectra measured at temperatures \(T=\) 2, 26 and 30 K under a weak-transverse field (wTF \(=20\) Oe) with the corresponding fits using Eq. (1) (solid lines). For clarity, \(A_0\) is the initial asymmetry and \(P_{\mathrm{TF}}(t)\) is the muon spin polarisation function. (b) Asymmetry plots as functions of temperature, where \(A_{\mathrm{TF1}}\), \(A_{\mathrm{TF2}}\) and \(A_{\mathrm{S}}\) are the initial asymmetries of the related polarisation components. Here the total wTF asymmetry is expressed as \(A_{\mathrm{TFtot}}=A_{\mathrm{TF1}}+A_{\mathrm{TF2}}\), which corresponds to the paramagnetic volume fraction of the sample. The sigmoid fit (red solid line) to the \(A_{\mathrm{TFtot}}(T)\) data yield the antiferromagnetic transition temperature \(T_{\mathrm{N}}\approx 27.1\) K. Data was recorded using the GPS instrument at PSI.