Tunable room-temperature soft ferromagnetism in magnetoceramics of organometallic dendrimers

Abstract

The development of new methods of assembling matter to access advanced materials, such as magnetoceramics, remains a worthwhile research challenge. Several approaches to generate such materials include pyrolysis of linear and hyperbranched polymer precursors. In this study, homometallic iron-containing (Fe), and heterometallic iron- and cobalt-containing (Fe–Co) dendrimers were used to generate magnetoceramics with tunable room temperature and soft ferromagnetism. The yet-to-be-explored dendritic precursors offer opportunities to control the magnetic properties via dendritic effects and functionalization with multiple ferromagnetic metals. Indeed, we tuned the magnetic properties of the homometallic ceramics via dendritic effects. Specifically, the saturation magnetization (M_s) and coercivity (H_c) decrease as the generation of the dendrimer increases. Incorporating Co into the dendrimers to synthesize heterometallic dendrimers noticeably changed the magnetic properties of the ceramics. M_s and H_c increased in ceramics derived from the second-generation dendrimer but these properties decreased in ceramics derived from zeroth- and first-generation dendrimers. The ferromagnetism in the homometallic and heterometallic ceramics differs in its response to changes in temperature. For instance, we observed that the homometallic ceramics were less susceptible to the changes in temperature, exhibiting a magnetic phase transition at ∼210 K in contrast to the heterometallic ceramics with a transition at ∼110 K. Overall, the results present dendrimers as a new type of precursors for magnetoceramics and expand the parameter space toward understanding magnetism in ceramics, allowing for the development of ceramics with tunable magnetism.