Controlled crystallization of Mn12 single-molecule magnets by compressed CO2 and its influence on the magnetization relaxation

6 pages, 6 figures, 2 tables.Micro- and sub-micro particles of complex [Mn12O12(O2CC6H5)16(H2O)4] ( 1) with controlled size and polymorphism have been prepared by dense-gas crystallization techniques, showing a remarkable particle size influence on the magnetization relaxation rates.This work was supported by DGI (Spain) under projects MAT2002-0043 and MAT2003-04699 and by the European Commission under the NoE MAGMANET (Contract NMP3- CT-2005-515767) and QUEMOLNA Marie Curie RTN (Contract MRTN-CT-2003-5044880). Javier Campo and Nora Ventosa thank the Ramon y Cajal Program of Ministerio de Educación y Tecnología (Spain) for their contracts. Maria Muntó thanks the Consejo Superior de Investigaciones Científicas (CSIC) for her PhD bursary and Jordi Gómez- Segura thanks the European Community for his PhD grant.Peer reviewe

Crystal size dependence of dipolar ferromagnetic order between Mn6 molecular nanomagnets

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

Forma pseudopolimórfica de hidrocloruro de nicardipina, procedimiento para su preparación y formulación que la contiene

Forma pseudopolimórfica de hidrocloruro de nicardipina, procedimiento para su preparación y formulación que la contiene. La presente invención se refiere a una nueva forma pseudopolimórfica de hidrocloruro de nicardipina, que en adelante se denominará Forma Dh, caracterizada por el difractograma de rayos X de polvo mostrado en la Tabla 1 y Figura 1, a un procedimiento para su preparación, al procedimiento para la obtención de un solvato de hidrocloruro de nicardipina, útil para la preparación de la nueva Forma pseudopolimórfica, y a la utilización de esta Forma Dh como medicamento y en la preparación de formulaciones farmacéuticas de liberación rápida de emergencia.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Università dell’InsubriaA1 Solicitud de patentes con informe sobre el estado de la técnic

Process for obtaining a composite

Filing Date: 2006-07-18.--Priority Data: ES P-200501747 (2005-07-19), US 60/716,113 (2005-09-12).-- Applicants: Activery Biotech, S.L. and Sociedad Española de Carburos Metálicos, S.A.The process for obtaining a micro- or nano- particulated composite comprises: adding at least two Compounds C to a fluid A, with one of said compounds being insoluble in said fluid A; adding a fluid B, such that said fluid B at working pressure Pw is miscible with said mixture A and acts as a co-solvent to form a solution AB, in which said pressure Pw is greater than atmospheric pressure but lower than the critical pressure Pc of the solution AB, and the working temperature Tw is lower than the critical temperature of the solution AB; and reducing the pressure Pw of said solution AB to atmospheric pressure, so that there occurs an increase of supersaturation that is ideally homogeneous throughout the solution AB and causes precipitation of the Compounds C. It also relates to the composite obtained

Controlled crystallization of Mn12 single-molecule magnets by compressed CO2 and its influence on the magnetization relaxation

6 pages, 6 figures, 2 tables.Micro- and sub-micro particles of complex [Mn12O12(O2CC6H5)16(H2O)4] ( 1) with controlled size and polymorphism have been prepared by dense-gas crystallization techniques, showing a remarkable particle size influence on the magnetization relaxation rates.This work was supported by DGI (Spain) under projects MAT2002-0043 and MAT2003-04699 and by the European Commission under the NoE MAGMANET (Contract NMP3- CT-2005-515767) and QUEMOLNA Marie Curie RTN (Contract MRTN-CT-2003-5044880). Javier Campo and Nora Ventosa thank the Ramon y Cajal Program of Ministerio de Educación y Tecnología (Spain) for their contracts. Maria Muntó thanks the Consejo Superior de Investigaciones Científicas (CSIC) for her PhD bursary and Jordi Gómez- Segura thanks the European Community for his PhD grant.Peer reviewe

Size-dependent dipolar ferromagnetism in micro- and nano-molecular crystals

Resumen del trabajo presentado a la XII Reunión del grupo de física de la materia condensada de la RSEF (GEFES), celebrada en Salamanca del 1 al 3 de febrero de 2023.We study experimentally how crystal size influences magnetic ordering in arrays of molecular nanomagnets coupled by dipolar interactions (Fig. 1, left). Compressed fluids techniques have been applied to synthesize crystals of Mn6 molecules (spin S = 12) with typical sizes ranging from 28 um down to 220 nm (Fig. 1, centre). The onset of ferromagnetic order and the spin thermalization rates have been studied by means of micro-SQUID ac susceptibility measurements. We find (Fig. 1, right) that the ordered phase remains ferromagnetic, as in bulk, but the critical temperature Tc decreases with crystal size. Simple magnetostatic energy calculations, supported by Monte Carlo simulations, account for the drop in Tc in terms of the minimum attainable energy for finite-size 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 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.Peer reviewe