Resonant effects in directly generated acoustic waves

Magnetic phase transitions in Gd64Sc36 studied using non-contact ultrasonics

“…EMATs consist of a coil of wire and an applied (bias) magnetic field, and their design has been described in detail elsewhere [13,15,16]. A current is pulsed through the coil, leading to a time-varying magnetic field, and when placed near a sample a mirror current or magnetisation change may occur within the sample; ultrasonic generation is therefore within the sample itself, rather than within the transducer.…”

“…Conventional ultrasonic measurements use piezoelectric transducers such as quartz or PZT to generate and detect ultrasound, however, these require the use of couplant and direct physical contact with the sample, [5][6][7][8] and with repeated thermal cycling the coupling between the transducer and the sample may quickly deteriorate. Electromagnetic acoustic transducers (EMATs) [10][11][12] offer a number of advantages, being non-contact, with narrowband or broadband operation possible through careful transducer design, and have previously been successfully employed to study phenomena such as giant quantum oscillations [13] and magnetic phase transitions [14,15], as well as being common in non-destructive testing applications [16].…”

Electromagnetic-acoustic conversion — a result of the action of a surface force

“…Этим определяется поста новка эксперимента по изучению деформационного механизма ЭМАП: измерения должны проводиться на образцах высокого качества при низких темпера турах на возможно более высоких частотах. Такие измерения проводились на полуметаллах -висмуте [4,18,[53][54][55][56] и сурьме [57], и на многих металлах -олове [5,58,59], галлии [60], алюминии [61,62], вольфраме [63][64][65], калии [66][67][68][69][70][71][72] и т.д. Мы не ставим своей целью дать полную картину современ ного состояния эксперимента и приведем здесь лишь несколько примеров экспериментальных исследова ний, в которых проявились основные черты дефор мационного механизма ЭМАП.…”