Muon site

Bm field at the muon site from internal J total electronic angular momentum... 

The field generated by a magnetic dipole jl at the vector distance r from the muon site is given by... 

High crystallographic symmetry of the moments surrounding the muon site can lead to complete cancellation of the dipolar field contribution to In a FM the imique domain magnetization will still generate Bcon, which then is the only source of if the material is... 

The simplest calculation involves the assignment of classical point-like ionic moments leading to an effective field and its distribution at the muon site, and it often provides an... 

It is important to stress once more that pSR measures the fluctuations of the localflelds at the muon site and not directly the fluctuations of the spins creating those fields. This means in essence that for a quantitative analysis (for TF as well as for ZF measurements) the exact relations between the individual components of lanthanide spin correlations S t)SfQ)) and the muon field correlations B t)B jS)) must be worked out for each particular muon spin -> lanthanide crystal geometry. This step is often overlooked. The general tensorial relation between spin and field correlation has been given by Dalmas de Reotier et al. (1996). 

The earlier pSR studies were concerned with the peculiar temperature dependence of the spontaneous precession frequency caused by the interplay of the isotropic contact field and the anisotropic dipolar field at the muon site. The latter is clearly dependent on the spatial alignment of the Gd spins. Also, the muon stopping site needed to be determined. These data will be discussed in sect. 4.2.2 below. Later studies included more detailed investigations of the dynamical critical behavior in the paramagnetic state (see following section). 

Fig. 31, Left Temperature dependence of local magnetic field at the muon site in ferromagnetic Gd at ambient and applied pressure (Schreier et al. 1997). Right Results of the detailed analysis of spectra in the spin turning regime. Two signals are present (open and solid symbols). Their meanings are described in the text (Hartmaim et al. 1994b). The lines are guides to the eye.

Fig. 38. ZF (iSR asymmetry spectrum from a single crystal of singlet-ground-state PrNij at 0.69 K (Kayzel et al. 1994), indicating well-defined local fields at the muon sites.

Fig. 56. Left ZF- and LF-(iSR spectra of polycrystalline DyAg at 18K. The solid lines are fits to a nearly static Lorentzian Kubo-Tc abe fiinction. Right Temperature dependence of distribution width and fluctuation rate of the field at the muon site as obtained from fils to the Lorentzian Kubo-Toyabe patterns seen in ZF data of cr-DyAg up to 51K. From Kalvius et al. (1986, 1990)...

The loss of sample signal for T magnetically inequivalent sites in the presence of a local axis of magnetization, leading to several different dipolar fields (Hartmann 1989) and in turn to rapid (static) depolarization. 

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