Macroscopic Quantum Phenomena in Nanomagnets and SQUIDs

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Macroscopic Quantum Phenomena in Nanomagnets and
SQUIDs
Jonathan FriedmanAmherst Collegewww.amherst.edu
/jrfriedman
Collaborators Amherst College Mustafa Bal (now
Dartmouth) UMass Yiming Chen, Qijun Xiao, Mark
Tuominen
Stony Brook Wei Chen UCSD Chemistry David
Hendricson, Evan Rumberger, Chris Beedle
Funding NSF, Alfred P. Sloan Foundation and
Amherst College Dean of Faculty
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Fe8O2(OH)12(tacn)6Br8.9H20
Fe3 S5/2
O N C
S10
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Double-Well Potential Nanomagnet
m -9
m -10
m 9
m 10

• Energy levels correspond to different
  orientations of the nanomagnet.
• Magnetic field tilts the double-well potential.

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Hysteresis loops for Mn12-ac Thermally Assisted
Tunneling of Magnetization

• J. R. Friedman et al., Phys. Rev. Lett. 76, 3830
  (1996).

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Equilibrium Magnetization of Fe8
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Equilibrium Magnetization of Fe8
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Pulsed Radiation Experiments
1.8 K

• M. Bal et al., Europhys. Lett 71, 110 (2005) and
  J. Appl. Phys., 99, 08D102 (2006).

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SQUIDs (Superconducting Quantum Interference
Devices)