Figure 4: Correlation between a remanent magnetic state of the magnetic film and the MC/MEL.

In these measurements the applied magnetic field plays an auxiliary role, and is used to write (‘set’) a particular remanent magnetic state, corresponding to a particular domain configuration and particular fringe-field pattern, and to erase (‘reset’) this configuration by replacing it with a saturated state without domains. This saturated state without domains is also used as the reference state against which we measure the MC and MEL percentage responses. Referring to the magnetization loop of an example magnetic film, (a) shows the procedure to set and reset different remanent states. The set field (blue star) is used to select a magnetic state. As the set field is being removed, the film remains in essentially the same state as evidenced by the only small amount of relaxation in magnetization between the write state (blue star) and remanent state (red star). (b) Conductance and (d) electroluminescence referenced to a fully saturated state measured in different magnetic states of the ferromagnetic film vs set field strength (red curve). For comparison, the conductance and electroluminescence value measured while the set field is still on is also shown (blue curve). Grey dashed curves correspond to measured values of conductance (b) and electroluminescence (d) at the set field when the magnetic film is saturated (blue and purple curves in Fig. 2). (c) Theoretical calculation following text, using switching fields from Fig. 1e, to be compared with d. Grey dashed curve is calculation with fringe fields absent.