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Alternatively, for the plasma model (8) Eq. (3) leads to 

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The magnitude of this reflection coefficient depends on the relationship between µ (0) and ω$_{p}$ . 

First we present the computational results for the Casimir interaction of two plates made of the ferromagnetic metal Co with [52] µ$_{Co}$ (0) = 70. Computations were performed at room temperature using Eq. (1) (the Casimir free energy per unit area of the plates) and Eq. (5) (the Casimir pressure). In all terms of these equations with l ≥ 1 we put µ ( iξ$_{l}$ ) = 1 in accordance with the results of Sec. II. In the zero-frequency terms, Eqs. (10) and (11) or (12) have been used depending on the chosen model of ε (Drude or plasma). For Co one has [60] ω$_{p,}$$_{Co}$ = 3 . 97 eV and γ$_{Co}$ = 0 . 036 eV. Below the computational results are presented as ratios to the zero-temperature Casimir energy per unit area and the Casimir pressure between two nonmagnetic parallel plates made of ideal metal, 

In Fig. 1, the solid lines show the values of F$_{Co}$ /E$_{0}$ (a) and of P$_{Co}$/P$_{0}$ (b) as functions of separation computed using the dielectric permittivity of the Drude model (7). In the same figure, the dashed lines show the computational results obtained with omitted magnetic properties of Co [i.e., with µ (0) = 1]. Quantitatively, the role of magnetic properties can be characterized by the ratio solid dashed 

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and by a similarly defined quantity η$_{P,}$$_{Co}$ . With the increase of separation distance from a = 0 . 5 µ m to 2 µ m and then to 6 µ m, η D F , Co varies from 17% to 63% and to 93%, respectively. At the same separations η D P, Co takes the following respective values: 12%, 44% and 92%. This permits us to conclude that when the Drude model is used to describe the dielectric properties of a ferromagnetic metal, the magnetic properties markedly (up to two times at large separations) increase the magnitude of the Casimir free energy and pressure. 

In Fig. 2(a,b) similar results for two Co plates described by the plasma model (8) are presented. The same notation as in Fig. 1 is used. As is seen in Fig. 2, for ferromagnetic metal described by the plasma model the impact of magnetic properties on the Casimir 

