Notizen: On a New Theory of the Magnetization Curve of Plastically Deformed Nickel Single Crystals

Abstract

Abstract A new theory of the magnetization process in plastically deformed nickel single crystals of single slip orientation is outlined. It is based on the interaction between the (101)-180°-domain walls and the three types of primary edge dis-location dipole and multipole arrangements dominating in stage I, in the transition region and in stage II of the stress-strain curve, respectively, i.e. the [121]-dipole bundles, the rope-like clusters of such bundles extended along [121], and the [121] -multipole walls, all having [T01]-Burgers-vectors. In increasing magnetic fields the primary edge dislocation arrangements are shown to be capable to glide to new ob-stacles under the pressure of the (101) -180°-domain walls which will follow them and whose segments at the same time start to vault themselves cylindrically or pillow-shapedly be-tween these dislocation barricades, finally overcoming them at the coercive force by Barkhausen jumps. In an earlier paper 1 first experimental results had been reported concerning the large decrease of num-ber and size of Barkhausen jumps observed on samples of plastically deformed nickel and on magnetite dur-ing simultaneously superposed intensive ultrasonic ir-radiation. To explain this unexpected effect in terms of domain wall motion, an attempt had been made to mo-dify the usual potential theory of the magnetization curve by introducting a new hypothetical magnetization process which should enable the domain walls also to move to some extent irreversibly and continuously but without Barkhausen jumps. In the meantime, the mentioned problems were sub-ject of a recently published extensive dissertation 2 which contains, in addition to a more detailed descrip-tion of the experiments and of the apparatus used, also the analysis of the main consequences of these experi-mental facts with respect to the usual potential theories of the magnetization curve of deformed nickel, showing the strong inconsistency between these theories on the one hand and the experimental results, reported in 1 and 2 , and certain other important empirical facts on the other. Last not least this dissertation contains a new consistent quantitative theory of the magnetization curve of plastically deformed nickel single crystals of single slip orientation. The aim of this note is to summarize in a qualitative manner the main statements of that new theory. Its basic assumptions which could be proved by quoting numerous experimental facts as well as by detailed quantitative estimations are the following ones: