Hysteresis, ferromagnetic

The instrumentation required to measure the hysteresis loop of a ferromagnetic surface with MOKE can be very simple. Figure 4a shows one such implementation of the experimental setup for analysis of ultrathin film samples maintained in a... 

Figure 1. Schematic diagram of a hysteresis curve for a typical ferromagnet showing magnetization (a) as a function of the applied magnetic field (H) Saturation magnetization Is Indicated by Os- Inset shows the multidomain structure and subdomain superparamagnetlc clusters.

Figure 2. Plot of relative magnetization, a/Os ns a function of H/T. (a) A paramagnetic system Is characterized by an effective magnetic moment, with a Bohr Magneton number vlO per Ion, and by the absence of hysteresis. Paramagnetic saturation occurs at very high "H/T" == 10 Oe K"l. (b) l.angevln curve for S.P. clusters, (c) Part of a ferromagnetic hysteresis curve.

It should be stressed that below a critical (Blocking) temperature (Tg) S.P. clusters will have a slow relaxation time (t) at which their net moment will align so-to-speak "parallel" to H, and thus appear to behave as if they had an apparent "bulk-like" ferromagnetic behavior. This aspect will result in a hysteresis or an "apparent" ferromagnetic behavior. Conversely, above the Tg, the hysteresis will disappear and the clusters will show a unique curve with no hysteresis (Fig. 2). 

Hysteresis curves for a magnetically hard and a magnetically soft ferromagnetic material. S = saturation magnetization, R = remanent magnetization, K = coercive force... 

Bean, C.P. (1955) Hysteresis loops of mixtures of ferromagnetic micropowders. Journal of Applied Physics, 26 (11), 1381-1383. 

Figure 3.32 Hysteresis behavior of the magnetization of a ferromagnetic crystal or polarization of a ferroelectric crystal with respect to the applied magnetic or electric switching field.

Fig. 13 A typical hysteresis curve for a sample with extended ferromagnetic coupling (see page 239).

S.P. Street, R. (1992) Evaluation of ferromagnetic materials for low frequency hysteresis heating of tumours. Phys. Med. Biol. 37 293-299... 

Figure 6.54 A hysteresis loop for a ferromagnetic materials. From K. M. Ralls, T. H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering. Copyright 1976 by John Wiley Sons, Inc. This material is used by permission John Wiley Sons, Inc.

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