National Synchrotron Light Source Seminar

Nuclear Magnetic Resonance Force Microscopy (NMRFM) is a
unique quantum microscopy technique, which combines the three-
dimensional imaging capabilities of magnetic resonance imaging (MRI)
with high sensitivity and resolution of atomic force microscopy (AFM).
It has potential applications in many dierent elds. This novel
scanned probe instrument holds potential for atomic-scale resolution.
MgB2 is a classic example of two-band superconductor. However
the behavior of these two bands below the superconducting transition
temperature is not well understood yet. Also the relaxation times of
single crystal MgB2 cannot be measured because it is not yet possible
to grow large enough MgB2 single crystals for conventional NMR.
Using our homemade NMRFM probe, we have set out to measure
the relaxation times of micron size MgB2 single crystals to answer
several questions relating to the anisotropy, multiband behavior, and
coherence eects in this unusual superconductor.
The main goal of the second project, the study of magnetic semi-
conductors, is to investigate magnetic properties of Mn-implanted
GeC thin lms. 20 keV energy Mn ions were implanted in two samples:
1) bulk Ge (100) and 2) a 250 nm thick epitaxial GeC lm, grown on
a Si (100) wafer by UHV chemical vapor deposition using a mixture
of germane (GeH4) and methylgermane (CH3GeH3) gases. A SQUID
magnetometer study shows ferromagnetism in both samples. While
the Curie temperature for both samples is about 180 K, the in-plane
saturated magnetic moment per unit area for the rst sample is about
2:210��5 emu/cm2 and that for the second sample is about 3:010��5
emu/cm2. These results show clear enhancement of magnetic proper-
ties of the Mn-implanted GeC thin lm over the identically implanted
Ge layer due to the presence of a small amount of carbon.