Dresden 2014 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 3: Magnetic/Organic Interfaces and Molecular Magnetism (organized by MA; with CPP, DS, HL, O, TT)
TT 3.2: Invited Talk
Monday, March 31, 2014, 10:00–10:30, HSZ 02
EPR Studies of Rare-Earth Molecular Nanomagnets — •Stephen Hill1, Sanhita Ghosh1, Dorsa Komijani1, Salvador Cardona-Serra2, Jose-Jaime Baldovi2, Yan Duan2, Alejandro Gaita-Arino2, and Eugenio Coronado2 — 1Department of Physics and NHMFL, Florida State University, Tallahassee, FL 32310, USA — 2ICM, Universidad de Valencia, 46980 Paterna, Spain
I will discuss the application of multi-frequency EPR to study the static and dynamic properties of a family of mononuclear Ln(III) (Ln = Ho or Tb) nanomagnets encapsulated in polyoxometallate (POM) cages. The encapsulation offers the potential for spintronics applications on surfaces or in devices, as it preserves the intrinsic properties of the nanomagnet outside of a crystal. A large magnetic anisotropy arises due to a splitting of the Hund’s coupled angular momentum (J = L + S) ground state in the POM ligand field. High-frequency EPR studies for the Ho(III) compound (J = 8) reveal an anisotropic eight line spectrum corresponding to transitions within the lowest mJ = ± 4 doublet, split by a hyperfine interaction with the I = 7/2 Ho nucleus. Meanwhile, X-band studies reveal the presence of a large tunneling gap (Δ∼9 GHz) within the mJ = ± 4 doublet. Spin-echo measurements allow studies of the coherent spin dynamics, including Rabi oscillations. Remarkably long T2 times are found, even for the most concentrated samples. It is postulated that this is due to the large gap, Δ, which provides an optimal operating point for coherent manipulations at X-band such that the quantum dynamics are relatively insensitive to dipolar fields.