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Magnetic properties and spin dynamics in the single-molecule paramagnets Cu(6)Fe and Cu(6)Co

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Title Magnetic properties and spin dynamics in the single-molecule paramagnets Cu(6)Fe and Cu(6)Co
 
Creator KHUNTIA, P
MARIANI, M
MOZZATI, MC
SORACE, L
ORSINI, F
LASCIALFARI, A
BORSA, F
MAXIM, C
ANDRUH, M
 
Subject relaxation
complexes
fe
cr
antiferromagnetic materials
cobalt alloys
copper alloys
diamagnetic materials
exchange interactions (electron)
ferromagnetic materials
hyperfine interactions
iron alloys
magnetic relaxation
magnetic susceptibility
magnetisation
molecular magnetism
paramagnetic resonance
proton magnetic resonance
spin dynamics
wave functions
 
Description The magnetic properties and the spin dynamics of two molecular magnets have been investigated by magnetization and dc susceptibility measurements, electron paramagnetic resonance and proton nuclear magnetic resonance (NMR) over a wide range of temperatures (1.6-300K) at applied magnetic fields H=0.5 and 1.5 T. The two molecular magnets consist of Cu(II)(saldmen)(H(2)O)}(6){Fe(III)(CN)(6)}](ClO(4))(3)center dot 8H(2)O in short Cu(6)Fe (here H saldmen is the Schiff base resulted by reacting salicylaldehyde with N,N-dimethylethylenediamine) and the analog compound with cobalt, Cu(6)Co. It is found that in Cu(6)Fe, whose magnetic core is constituted by six Cu(2+) ions and one Fe(3+) ion all with s=1/2, a weak ferromagnetic interaction between Cu(2+) moments through the central Fe(3+) ion with J=0.14 K is present, while in Cu(6)Co the Co(3+) ion is diamagnetic and the weak interaction is antiferromagnetic with J=-1.12 K. The NMR spectra show the presence of nonequivalent groups of protons with a measurable contact hyperfine interaction consistent with a small admixture of s wave function with the d function of the magnetic ion. The NMR relaxation results are explained in terms of a single-ion (Cu(2+), Fe(3+), Co(3+)) uncorrelated spin dynamics with an almost temperature-independent correlation time due to the weak magnetic exchange interaction. We conclude that the two molecular magnets studied here behave as single-molecule paramagnets with a very weak intramolecular interaction, almost on the order of the dipolar intermolecular interaction. Thus they represent a separate class of molecular magnets which differ from the single-molecule magnets investigated up to now, where the intramolecular interaction is much larger than the intermolecular one.
 
Publisher AMER PHYSICAL SOC
 
Date 2011-07-16T21:53:07Z
2011-12-26T12:49:58Z
2011-12-27T05:35:50Z
2011-07-16T21:53:07Z
2011-12-26T12:49:58Z
2011-12-27T05:35:50Z
2009
 
Type Article
 
Identifier PHYSICAL REVIEW B, 80(9), -
1098-0121
http://dx.doi.org/10.1103/PhysRevB.80.094413
http://dspace.library.iitb.ac.in/xmlui/handle/10054/4538
http://hdl.handle.net/10054/4538
 
Language en