Experimental studies of structurally incommensurate crystal phases

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=620512

Effect of roughness, frustration, and antiferromagnetic order on magnetic coupling of Fe/Cr multilayers

Structure–property relationship studies have been performed in the La-modified lead zirconate titanate (PLZT) solution as a function of quenched La impurity content and Zr/Ti ratio by transmission electron microscopy, lattice imaging, and dielectric spectroscopy. Investigations were performed for 65/35⩽Zr/Ti⩽90/10. These investigations have demonstrated a general trend in domain structure and polar order with increasing quenched impurity concentration. For Zr/Ti ratios of 90/10 and 85/15, a structurally incommensurate antiferroelectric (AFEin) state was found to be stabilized with increasing La. Temperature dependent investigations demonstrated that the incommensurate structure becomes pinned into long-time metastable states, rather than transforming to a commensurate phase. Also, the modulation wavelength (λ) was found to increase significantly with increasing Ti. When λ increased to ∼40 A, polar clusters began to condense from the AFEin order. For Zr/Ti ratios of 80/20 and 65/35, increasing quenched dis...

Effects of quenched disorder on La-modified lead zirconate titanate: Long- and short-range ordered structurally incommensurate phases, and glassy polar clusters

Cooperative magnetic properties in single- and two-phase 3d metallic alloys relevant to exchange and magnetocrystalline anisotropy

The present state of the theory and the main experimental results are reviewed for systems in which the antiferromagnetic ordering is directly due to a peculiar topology of the Fermi surface, i.e., to the presence of nested electron and hole sheets. A familiar example of such a system is chromium, which supports a spin-density wave (SDW) that is incommensurate with the lattice. For this reason much of the experimental material discussed in this review is for chromium and its alloys with transition and nontransition metals. The theoretical description of SDWs of this type is based on the excitonic insulator model, which is discussed in detail not only in connection with the phase diagrams and SDW structure but also in regard to the electronic properties of systems of this type (measurements of the de Haas-van Alphen effect, optical measurements, band-structure calculations from first principles, etc.). The review concludes with a discussion of less-studied transition-metal compounds which apparently also support a SDW state due to a peculiar topology of the Fermi surface.

https://iopscience.iop.org/article/10.1070/PU1984v027n12ABEH004088/pdf

Spin-density waves and itinerant antiferromagnetism in metals

The incommensurate-commensurate phase transition of CrMn single crystals is shown to be of first order. Coexistence of the two phases reported in the past is shown conclusively to be due to inhomogeneities in the Mn concentration of large samples. The observed relative length changes and latent heat effects at the transition correlate well with the known pressure dependence of the transition temperature. At this temperature very small resistivity anomalies are present as a result of a different temperature dependence of the resistivity of the incommensurate and commensurate phases.

G Benediktsson

Papers

On the first-order incommensurate-commensurate phase transition of CrMn single crystals