*Article* **Field-Induced Transition in (Nd,Dy)2Fe14B in Ultrahigh Magnetic Fields**

**N. V. Kostyuchenko 1,\*, I. S. Tereshina 2, A. I. Bykov 3, S. V. Galanova 3, R. V. Kozabaranov 3,4, A. S. Korshunov 3, I. S. Strelkov 3, I. V. Makarov 3, A. V. Filippov 3, Yu. B. Kudasov 3,4, D. A. Maslov 3,4, V. V. Platonov 3,4, O. M. Surdin 3,4, P. B. Repin 3, V. D. Selemir 3,4 and A. K. Zvezdin 5,6**


**Abstract:** We demonstrate the peculiarities of the magnetization process in the ferrimagnetic intermetallic compound (Nd0.5Dy0.5)2Fe14B, which has been studied theoretically and experimentally using ultrahigh magnetic fields. We observe phase transition induced by external ultrahigh magnetic fields (up to 170 T) and also describe the magnetization process analytically in terms of critical transition fields. In this work, the first and second critical fields of the field-induced magnetic transitions, *H*c1 and *H*c2, were estimated, and the results were verified against experimental data for *H*c1. Critical field *H*c2 predicting the place of transition to the forced-ferromagnetic state was estimated for the first time for (Nd0.5Dy0.5)2Fe14B compound. A comparison of the magnetization behavior for (Nd0.5Dy0.5)2Fe14B with the basic systems Nd2Fe14B and Dy2Fe14B is also performed. We demonstrate that, in the Dy2Fe14B compound, the field-induced transition type is changed from the first to the second order due to the replacement of the Nd atom by Dy one.

**Keywords:** complex modified materials; critical fields; exchange coupling; hard magnetic materials; ultrahigh magnetic fields; R–Fe exchange; rare-earth intermetallics
