Effect of structural defects on the magnetic properties of the EuBaCo$_{1.90}$O$_{5.36}$ single crystal

The effect of structural defects in cobalt and oxygen sublattices with the constant average oxidation level 3+ of all cobalt ions on the magnetic properties of the EuBaCo$_{1.90}$O$_{5.36}$ single crystal has been studied. The magnetic properties of the single crystal and the polycrystalline sample of the corresponding composition are compared in the range $T$ = 200–650 K. The results show that the cobalt-deficient EuBaCo$_{2-x}$O$_{5.5-\delta}$ samples demonstrate a three-dimensional $XY$ ferromagnetic ordering of magnetic sublattices. The values of the effective magnetic moment at $T>$ 480 K indicate the existence of the $IS$ and $HS$ states of Co$^{3+}$ ions. The large difference of values of $\mu_{\operatorname{eff}}$ of the EuBaCo$_{1.90}$O$_{5.36}$ single crystal and polycrystal can be due to that the magnetic ion spins lie in plane $ab$. The magnetic field directed along plane $ab$ substantially influences the magnetic ordering at $T<$ 300 K.