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Hysteresis loops measured at end 1 (see schematic diagram of the set-up in right inset) of the micro-crystal at different temperatures for parallel to the EMD. The measurements were carried out at an external field sweep rate of 50 mT/min. Shown in the left inset are a set of data obtained by sweeping the field at a slow rate of 1 mT/min, where stochastic Barkhausen jumps, in addition to a non-stochastic jump at = 20 mT, are clearly visible.
(a) Magnetic stray fields measured for = 0.1 T of the micro-crystal obtained from vs. isotherms in Fig. 1 (filled circles, the line is a guide to the eye) and from continuous temperature sweep measurements for and , respectively. The dashed line shows the derived Bloch's behavior. The deviation from Bloch's law is shown clearly in the inset which shows . The straight line in the inset is a linear fit of vs. data. (b) SQUID measurements of M vs. T of a bulk pellet (from which the single grain was picked) showing a feature at around 60 K for an external field of 1 mT. The magnetization at large field follows Bloch's law, as shown in the inset. (c) M vs. T for pure powder showing a minimum at .
(a) A representative hysteresis loop measured at T = 90 K and (b) the enlarged plot showing a few resolved Barkhausen jumps. The two jumps marked by arrows and the corresponding noise level are shown in the inset. The noise level in the figure is of the order of the size of the data points. (c) Sum of the amplitudes of all individual Barkhausen jumps at one end of the micro-crystal observed at different temperatures. Inset of (c) shows the total Barkhausen jump amplitude normalized by the total number of jumps observed at different temperatures. The dotted lines are guides to the eyes.
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