Due to this microstructure, some unique magnetic properties are found in this type of tape. As an example we show three different tapes, evaporated under the same conditions except for the oxygen flow. Their magnetic behaviour can be analysed on the following three different levels.
The basic macroscopic characteristics are shown in
the following table, containing VSM and
Torque measurements. Note that
an additional sample where no oxygen was added to the process,
which was prepared under identical circumstances, showed only
an longitudinal coercivity of 6 [kA/m].
| A | 2.5 | 37 | 641 | 188 |
| B | 5.0 | 28 | 342 | 160 |
| C | 10 | 35 | 277 | 172 |
Recording experiments show the following ouput versus frequency behaviour of the three tapes (Figure 11). From this graph, the existence of an optimum oxygen concentration can be concluded.
Also the so called good and bad recording directions
can be observed as shown in figure 12. At about 9 MHz the first
gap-null of the head can be observed.
Figure 12: Output versus frequency curve of a ME tape where the turning direction of the tape has been changed. This gives rise to the "good" and "bad" recording directions. |
MFM observations confirm what was already known from recording experiments, namely the existence of so called "good" and "bad" recording directions. Figure 13 shows the evidence of this hypotheses with a written track (labda =1 µm) in Metal Evaporated tape.
The explanation of the effect is that the leading
edge of the head field writes a bit where as the trailing edge
partly erases the written bit again. If the trailing edge field
is directed in the hard axis of the tape, the erasure effect is
smaller as if it is in the easy axis of the ME tape.
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Figure 13: | 
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