Figure 4: Monopole signatures.
From: Brownian motion and quantum dynamics of magnetic monopoles in spin ice
The experimental variance in logarithmic relaxation time 
(circles, errors bars represent s.d.) compared with the predicted form for monopolar-field assisted tunnelling. Red and green indicate, respectively, applied fields of 
and the set of finite fields listed in the caption of Figure 3. For each curve there are two fitted parameters 
and 
, which describe the mean square static field and mean square monopole field, respectively. The line is the function 
where x(T) is the monopole density. The shading indicates the maximum possible systematic error (absolute minima and maxima) in the monopole density. We find σ1,2=0.84(1),3.40(5), respectively, in zero field and 1.15(1),3.40(5) in finite field. The deviation at T>10 K is related to a change in relaxation mechanism (see text).
