Mn-based room-temperature ferromagnets attract considerable attention due to their high ordered Mn moment. We have found that a Pd 0.75 Mn 0.25 alloy with added B (Pd 0.75 Mn 0.25 B x ) shows room-temperature soft ferromagnetism, whereas the parent Pd 0.75 Mn 0.25 alloy is a spin-glass system.The saturated Mn moment at room temperature systematically increases to 2.68µ B /Mn as x increases to 0.125. The maximum Curie temperature of 390 K is also realized at an x of 0.125. The experimental results suggest a tunable soft ferromagnetism, which is governed only by the boron concentration.Our results will pave the way in chemical control of room-temperature bulk ferromagnetism in Mn compounds based on the addition of an atom with a small atomic radius.

Interstitial light elements play an important role in magnetic materials by improving the magnetic properties through changes of the unit cell volume or through orbital hybridization between the magnetic and interstitial atoms. In this review focusing on the effects of interstitial atoms in Mn-based compounds, which are not well researched, the studies of interstitial atoms in three kinds of magnetic materials (rare-earth Fe-, Mn-, and rare-earth-based compounds) are surveyed. The prominent features of Mn-based compounds are interstitial-atom-induced changes or additional formation of magnetism—either a change from antiferromagnetism (paramagnetism) to ferromagnetism or an additional formation of ferromagnetism. It is noted that in some cases, ferromagnetic coupling can be abruptly caused by a small number of interstitial atoms, which has been overlooked in previous research on rare-earth Fe-based compounds. We also present candidates of Mn compounds, which enable changes of the magnetic state. The Mn-based compounds are particularly important for the easy fabrication of highly functional magnetic devices, as they allow on-demand control of magnetism without causing a large lattice mismatch, among other advantages.

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