Casimir free energy and pressure under the magnetic phase transition which occurs with the increase of temperature in the configuration of two similar plates made of ferromagnetic metals. As such a metal, here we use Gd. The reason is that Co and Fe used in com- putations of Secs. III and IV possess rather high Curie temperatures (1388 K and 1043 K, respectively [71]). Keeping in mind that it is hard to measure the Casimir force at such high temperatures, we consider Gd which Curie temperature is of about 290 K depending on the treatment of a sample (see, e.g., [72, 73]). In the literature, Gd is often discussed in connection with its ferromagnetic properties, and the admixtures of Gd atoms are included in different materials (see, e.g., [74, 75]). The Drude parameters of Gd are equal [76] to ω$_{p,}$$_{Gd}$ = 9 . 1 eV, γ$_{Gd}$ = 0 . 58 eV. Computations of the Casimir free energy and pressure in the configuration of two Gd plates as functions of temperature in the vicinity of Curie temperature require respective values of µ (0) for Gd at T < T$_{C}$ [at T > T$_{C}$ , µ$_{Gd}$ (0) = 1 to high accuracy]. In Fig. 12, using the data [75], we model the approximate dependence of µ$_{Gd}$ (0) in the temperature region from 280 K to 300 K. Then the Casimir free energy and pressure were computed as functions of temperature using Eqs. (1) and (5) with above values of the Drude parameters. The computational results for the Casimir free energy are presented in Fig. 13(a) and for the Casimir pressure in Fig. 13(b) at separation a = 500 nm. In both figures (a) and (b) the solid and dashed lines marked 1 and 2 indicate the results computed using the Drude and plasma model for the characterization of the dielectric permittivity of Gd, respectively. As in previous sections, the solid lines take into account the magnetic properties of Gd. The dashed lines were computed with magnetic properties disregarded. As can be seen in Fig. 13(a,b), at T > T$_{C}$ the magnetic properties do not influence the Casimir free energy and pressure. At the same time, the Drude and plasma model approaches lead to results differing for about –23.4% for the Casimir free energy and –19.5% for the Casimir pressure. The computational results at T < T$_{C}$ are of special interest. Here, the magnetic properties influence the Casimir free energy and pressure. Below of about 288 K this influence is almost temperature-independent. Quantitatively, at T = 280 K the relative influence of magnetic properties on the Casimir free energy is η D F , Gd = 11 . 6% if the Drude model is used and η p F , Gd = − 3 . 6% if computations are done by means of the plasma model. Similar situation holds for the Casimir pressure. Here, the relative influence of magnetic properties is characterized by η D P, Gd = 7 . 4% for the Drude model and η p P, Gd = − 3 . 3% for the plasma 22