Slow Magnetic Relaxation in Co II Cu II Coordination Oligomer Built into Mesoporous Material

The ferrimagnetic system CoCu(opba) [opba = ortho ‐phenylenebis(oxamato)] was employed to prepare a traditional chain [CoCu(opba)] · 4H 2 O ( 1 ) and a nanocomposite by incorporation in porous Vycor glass (PVG). This nanocomposite was made by first anchoring [Bu 4 N] 2 [Cu(opba)] on PVG [PVG‐Cu ( 2 )] and then treating it “in situ ” with cobalt(II) acetate to obtain the nanomagnet PVG‐CuCo ( 3 ). Magnetic measurements show that 1 consists of a one‐dimensional ferrimagnet with strong intrachain antiferromagnetic coupling and weak interchain interactions that result in spin‐glass behavior below 3.5 K. Nanocomposite 3 presents ferrimagnetic chains limited by the nanopore size, which leads to a slow relaxation of the magnetization following Arrhenius' law, frequency dependence for in‐phase and out‐of‐phase susceptibility, and hysteresis below the blocked regime temperature (< 6 K). These features are characteristics of single‐chain magnets (SCM).(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)