Hysteresis curves

**Table 4:** Magnetic properties
Sim.	Simulation	red. Polarization	Coercivity
#	name	J/J_s	[kA/m]
1	hex_Ia1m1	0.702	1190
2	hex_Ia1m2	0.717	1006
3	hex_Ia2	0.506	670
4	hex_Ia3	0.804	1341
5	hex_Hm1	0.631	1190
6	hex_Hm2	0.638	1006
7	hex_T	0.601	838

The results show, that the finer mesh of finite elements (hex_Ia1m2 and hex_Hm2 as compared to hex_Ia1m1 and hex_Hm1) leads to an increase in remanence and a decrease in coercivity. The difference is only a few percent and does not pay for the increase in CPU time as indicated in table 5 on page

, if one is only interested in those values. However, since it was unknown if the effect of interaction between the particles would be visible at all, the fine element mesh has been used in the rest of the simulations.

Also the effect of anisotropy on remanence and coercivity is illustrated in the above table.

The uniformly distributed anisotropy axes of hex_Ia1m1 and hex_Ia1m2 result in values for remanence and anisotropy which are between hex_Ia2 and hex_Ia3. The anisotropy axes in hex_Ia3 lead to a preferred direction closer to the long axis of the particle than in hex_Ia3. Thus, the remanence and anisotropy are increased. hex_Ia2 contains many misaligned particles which make the magnetic properties worse.

The interaction between the particles causes a slight decrease in remanence. If the particles of hex_Ia2 and hex_Ia3 were independent, the remanence of the two particle system could be expected to be the arithmetic mean of the values for the single particles. However, the result of hex_Hm2 (0.638) is lower than the expected value of 0.655, which can be attributed to the interaction of the particles.

For the T-shape arrangement the remanence is even lower. The reason being the misalignment of the second particle with its long axis perpendicular to the external field. As a result, the coercivity drops as well.

**Figure 11:** Demagnetization curves
$\begin{figure} \centering \subfigure[{\sf hex\_Ia1m1}]{ \includegraphics[scale... ...e[{\sf hex\_T}]{ \includegraphics[scale=0.6]{fig/inthexh.hys.eps} }\end{figure}$

**Figure 12:** Comparison of *hex_Ia1m2*, *hex_Ia2*, and *hex_Ia3*
$\begin{figure} \centering \includegraphics[scale=0.8]{fig/cmpIa1m2Ia2Ia3.eps}\end{figure}$

**Figure 13:** Comparison of *hex_Hm2*, *hex_Ia2*, and *hex_Ia3*
$\begin{figure} \centering \includegraphics[scale=0.8]{fig/cmpHm2Ia2Ia3.eps}\end{figure}$

**Figure 14:** Comparison of *hex_Ia1m2*, *hex_Hm2*, and *hex_T*
$\begin{figure} \centering \includegraphics[scale=0.8]{fig/cmpIm2Hm2T.eps}\end{figure}$