Glassy state formation and magnetic properties of Co-rich ternary RE–Co–B (RE = Y, Tb, Ho) amorphous alloys

• Y–B alloys possess the highest GFA as a result of large atomic size mismatch.
• Significant thermal stability of amorphous structure.
• Sperimagnetic behavior for Ho- and Tb-containing samples.
• −ΔSm maxima on H2/3 dependence indicates the second-order phase transition.

Glass forming abilities (GFA) of a ternary Y–Co–B system and its sub-binaries were calculated on the basis of semi-empirical Miedema’s and geometric models. Formation enthalpies of amorphous alloys, their solid solution counterparts and the differences between both were determined and discussed. As any additional alloying element promotes formation of glassy states, ternary alloys should be favored according to the empirical rules. However, in investigated ternary system atomic radius difference between Y and B is a deciding factor. Respectively, normalized mismatch entropy and glass forming ability parameter ΔPHS indicate the Y27B73 and Y35B65 compositions, as the best glass formers. Co-rich melt-spun RE–Co–B (RE = Y, Tb, Ho) ribbons with high GFA were prepared by rapid quenching to analyze their magnetic properties and the effect of rare earth element substitution on magnetic entropy changes. Magnetization vs. temperature curves indicate the ferromagnetic ordering in Y-containing alloy and sperimagnetic behavior for other amorphous alloys, due to the antiferromagnetic coupling between Co and rare earth element sublattices. Linear dependence of −ΔSm maxima on H2/3 is reported as a verification of second-order magnetic transition.