. The Bell System technical journal . (H — He) seemed to occur at a somewhat higher temperature. Thisdifference may be due to slight variations in composition among the a. 6 UJ 2 T = 201°K ^ V = 26,150() y y/X) ^ z^ /^ HpRi IN OERSTEDS applied field. T\])ical plot of actual data for doiiiaiii wall velocity as a Iuiictioii of 1036 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 samples (Chemical analysis indicated that Sample 1 was (NiO)(FeO),as distinct from (NiO)(FeO) for Sample 4) but it is possible that other more subtle
. The Bell System technical journal . (H — He) seemed to occur at a somewhat higher temperature. Thisdifference may be due to slight variations in composition among the a. 6 UJ 2 T = 201°K ^ V = 26,150() y y/X) ^ z^ /^ HpRi IN OERSTEDS applied field. T\])ical plot of actual data for doiiiaiii wall velocity as a Iuiictioii of 1036 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 samples (Chemical analysis indicated that Sample 1 was (NiO)(FeO),as distinct from (NiO)(FeO) for Sample 4) but it is possible that other more subtle differences such asthe arrangement of the divalent nickel and iron ions are involved. Volt-ages induced in the secondary winding on Sample 3 for various appliedfields were much higher than for the other samples at room confirms the presence of more than one wall as indicated by thedomain pattern. Therefore no further data were taken on this sample, after it had been cooled to the temperature of lic^uid. 100 200 300 400 TEMPERATURE IN DEGREES KELVIN Fig. 8 — Plot of v/{H — He) for Sami)]e 4 as a function of temperature. MOTION OF INDIVIDI Al. DOMAIN WALLS 1037 5 300 O 200O •y T=77 K y o O ^^ y-c) = 160 () ^- ^ 1<^ 0. HpRI 8 N OERSTEDS Fig. 9 — Plot of wall velocity as a function of applied field at 77°K. Note thatat the higher fields the velocity is no longer a linear function of the applied field. air once, gave the same value of vfijl — H^ as before. Samples 1 and 2,howe^er, were cooled several times, and after the later runs they nolonger did tliis. In both cases the value of v/{H — He) as deduced fromthe ideal domain pattern and (1) was lower by about one-half; we inter-pret this to mean that the domain pattern in these samples was changedby the repeated thermal shock. Direct confirmation of this interpreta-tion by observation was not possible, however, for reasons mdicatedabove in connection \\\
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