in which ˜ P and ˜ M may be evaluated from Eqs. (5) and (10). In Fig. 6 and 7 we plot the calculated temperature dependences of the susceptibilities mentioned above. The magne- toelectric coupling causes the enhancement of polarization around T$_{RM}$ and a suppression of the dielectric constant cf. Fig. 6. One can see that at zero applied magnetic field ˜ χ$_{e}$ decreases stepwise at T$_{RM}$ whereas it is gradually suppressed with increasing field. χ$_{e}$ ( T ) exhibits a trend observed experimentally with increasing H$_{a}$ , but the calculated changes are too large. However, the corresponding temperature range is reproduced to much bet- ter accuracy than that of [20], where the calculated temperature T$_{RM}$ is far too low. The magnetic-susceptibility data follow roughly the Curie-Weiss law with the paramagnetic Curie temperature Θ$_{M}$ ≈ 120 K . Only the dashed curve in Fig. 7 reproduces correctly the approx- imate Curie-Weiss law at high temperature. This unusual behavior from a magnetic point of view can be understood easily from Eq. (28), where the nonlinearity in magnetization (the term ∝ ˜ M $^{2}$) can be dominated by the magnetoelectric coupling, as T$_{f}$/T$_{M}$ >> 1. FIG. 6: Dielectric susceptibility as a function of temperature for the specific values of applied magnetic field. C. Arrot planes In systems with one order parameter a convenient way to represent their behavior near the phase transition temperature is to draw Arrot plots. For a ferromagnet, the Arrot plot is a series of curves M 2 vs. H$_{a}$/M . The same approach can be used in our case with two order parameters. The only difference is that now instead of having a series of curves we 12