2026-04-17T18:08:54Zhttps://recercat.cat/oai/request

oai:recercat.cat:2445/1929222025-12-04T21:40:23Zcom_2072_1057col_2072_478917col_2072_478933

00925njm 22002777a 4500 dc Burzurí, Enrique author Martínez Pérez, María José author Muntó, Maria author Barrios Moreno, Leoní Alejandra author Ventosa, Nora author Roubeau, Olivier author Veciana, Jaume author Aromí Bedmar, Guillem author Fernández, Luisa author 2023-02-01T10:12:49Z 2023-02-01T10:12:49Z 2022-11-28 2023-02-01T10:12:49Z We study how crystal size influences magnetic ordering in arrays of molecular nanomagnets coupled by dipolar interactions. Compressed fluid techniques have been applied to synthesize crystals of Mn6 molecules (spin S=12) with sizes ranging from 28μm down to 220 nm. The onset of ferromagnetic order and the spin thermalization rates have been studied by means of ac susceptibility measurements. We find that the ordered phase remains ferromagnetic, as in the bulk, but the critical temperature Tc decreases with crystal size. Simple magnetostatic energy calculations, supported by Monte Carlo simulations, account for the observed drop in Tc in terms of the minimum attainable energy for finite-sized magnetic domains limited by the crystal boundaries. Frequency-dependent susceptibility measurements give access to the spin dynamics. Although magnetic relaxation remains dominated by individual spin flips, the onset of magnetic order leads to very long spin thermalization time scales. The results show that size influences the magnetism of dipolar systems with as many as 1011 spins and are relevant for the interpretation of quantum simulations performed on finite lattices. Creixement cristal·lí Nanoestructures Crystal growth Nanostructures Crystal size dependence of dipolar ferromagnetic order between Mn6 molecular nanomagnets