Broadband ultrasonics applied to phase transition characterisation in chromium antiferromagnetic alloy

Ultrasonic pulse-echo techniques are being widely used in the investigation of magnetic phase transitions in solid materials. In general, changes in the ultrasonic pulse amplitude and velocity are measured, and then the ultrasonic attenuation and elastic constants are determined for fixed frequencie...

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Bibliographic Details
Published in:Scripta materialia 2001-05, Vol.44 (10), p.2373-2378
Main Authors: de Camargo, Paulo Cesar, Krüger, Silvio Elton, Rebello, João Marcos Alcoforado
Format: Article
Language:English
Subjects:
Acoustic methods
Antiferromagnetics
Applied sciences
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
Magnetic properties and materials
Magnetic structure
Metals. Metallurgy
Nondestructive testing
Phase transformations
Physics
Studies of specific magnetic materials
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Summary:Ultrasonic pulse-echo techniques are being widely used in the investigation of magnetic phase transitions in solid materials. In general, changes in the ultrasonic pulse amplitude and velocity are measured, and then the ultrasonic attenuation and elastic constants are determined for fixed frequencies given by the odd harmonics of the transducer coupled to the sample. It is difficult to reproduce the same conditions of coupling between transducer and sample, therefore most analyses are limited to a few fixed frequencies. An investigation of the ultrasonic pulse propagation close to a magnetic phase transformation, for a continuous frequency range, is presented using wide band transducers and digital spectral analysis. The material chosen is a single crystal of Cr-0.18at%Re, which has a magnetic phase transformation from the paramagnetic (PM) to an antiferromagnetic (AFM) state at 318 K. Similarly to pure chromium, the ultrasonic attenuation and internal friction for this alloy have a contribution due to the coupling between the spin density wave in the AFM phase and the oscillatory elastic strain introduced by the ultrasonic pulse. Since the sixties the ultrasonic broadband analysis is being widely used for many applications. In this paper, we have shown that the ultrasonic spectral analysis approach is highly advantageous in many aspects for the investigation of phase transitions.
ISSN:1359-6462
1872-8456
DOI:10.1016/S1359-6462(01)00944-7