- Conference date: 13–16 November 1973
- Location: Boston, Massachusetts
The magnetic phase diagram of DAG has been of interest recently because it appeared to possess a tricritical point in a readily accessible region of field and temperature ( , ). The first order region below Tt is of special interest since the paramagnetic and antiferromagnetic phases coexist over a range of applied field by virtue of demagnetizing effects. It is thus possible to study the transition in some detail. Recently we have reported optical studies of DAG in this region. These comprised measurements of magneto‐optical rotation as a function of field and temperature as well as microscopy of the mixed phase. Here we present further results of the microscope studies. Our samples were thin (111) sheets (25–200μm thick) with the field along . The two phases are distinguishable by virtue of their different Faraday rotations (e.g. at for ). On entering the mixed phase from the high or low field boundaries, nuclei of the new phase appear, then rapidly grow to extend all the way through the specimen. Soon this structure apparently breaks up into separate needles of the new phase, which repel each other. A complicated evolutionary process develops over a long period of time, greater than 1000 seconds, and a final state is reached in which the two phases are very finely intermixed on a scale of less than 3μm. In the center of the coexistence region the two phases seem disposed in a sponge‐like fashion. As in the more familiar growth of crystals from a liquid the details of the magnetization structure seen at any point in field and temperature depend greatly on the way in which that point was reached. A detailed report of this work will be published elsewhere.
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