AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Invited Paper MI-ThA3
High Frequency Investigations of Molecular Nanomagnets by use of a Broadband SQUID-Detected Electron Paramagnetic Resonance Probe

Thursday, November 18, 2004, 2:40 pm, Room 304A

Session: Molecular Spintronics and Dynamics
Presenter: B. Cage, National Institute of Standards and Technology
Authors: B. Cage, National Institute of Standards and Technology
S.E. Russek, National Institute of Standards and Technology
D. Zipse, Florida State University
J.M. North, Florida State University
N.S. Dalal, Florida State University
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We are synthesizing and characterizing (by use of high frequency electron paramagnetic resonance (HFEPR)) molecular nanomagnets (magnetic molecules < 2 nm that behave as single molecule magnetic domains) for high-frequency spintronics applications. We will discuss current efforts to examine the magnetic susceptibility of these nanomagnets as 2-dimensional films vs the 3-dimensional bulk behavior of aligned single crystals. HFEPR data at 95 and 141 GHz, with magnetic resonance fields ranging from 0 - 12 Tesla indicate potential as tunable high-frequency low-applied-field oscillators from 5 - 80 K. This work represents some of the highest temperatures at which these magnets have been characterized, which is of importance for practical spintronics applications. To complement this work we have developed a new experimental technique that uses SQUID detection of the magnetic susceptibility as a function of applied magnetic field through the EPR transition at resonance frequencies > 60 GHz and magnetic fields up to 5 Tesla. One advantage over conventional EPR being the quantitative determination of the level of saturation. We will present data on the large electronic spin (S) S=10 molecular nanomagnet Fe8 that discretely identifies the spin-lattice-relaxation time, T1, of the individual ms quantum spin states. This is in contrast to the current non-resonant techniques, such as AC susceptibility, that only provide information on the global T1 properties averaged across all states.