1) MR dependence on temperature: a) Movement of switching fields from overlapping H=0 at high temp to separated
and apart at low temp. (working theory: VT interlayer has extra spins causing AF coupling at high temp state)
b) MR dependence on temp: increases as expected when temp. decreasesc) Thermal hysteresis: Switching field movements (described above in a) have a
temperature history (quantitatively different behaviors based on different cooling runs – working theory: thermal quenching)
2) MR dependence on bias (I-V shows interface dipoles are present): a) Non-monotonic MR effect based on bias in G-V plots (never been seen before)
a) Off-zero peak of G-Vb) Bias direction dependence of magnetic sweeps
b) Hysteretic pockets in the G-V curves (working theory: trapped spin states in low-spin VT)
c) At low temp, the switching field movement (towards H=0) can also be driven by a higher bias (higher energy causes reversion back to high spin?)
3) Light: At low temp, light can cause transition back to AF coupling behavior (switching fields move back across H=0 – consistent with transition back to high-spin state)
List of Key Findings for VT Paperfrom sample CC149
5-19-12
Figure 1: Switching Fields change as a function of temperatureAt high temp, coercive fields overlap (AF coupling via extra spins in the high-spin CoII form of the molecule). At low temp, the layers are again switching independently (no coupling in the low-spin CoIII form of VT).
Figure 1
Figure 2
Figure 2: Non-monotonic MR as a function of bias. Also shown are hysteretic trapped states.
Figure 3: Light experiment at 80K. Turning on the laser causes the AF coupling to return.
Figure 3
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