document: It is known that as the temperature of the sample rises, the Lorentz mechanism remains dominant until Tc of steel is reached (770°C for a low carbon steel), when the magnetostrictive mechanism becomes more efficient [15]. Previously this has been thought due to a thin ferromagnetic oxide layer on the sample surface, the surface being cooler than the bulk of the material [16,17]. This layer concentrates the magnetic field, increasing generation efficiency. Recent studies also show that rearrangement of the magnetic moments from ordered domains to a disordered state at a magnetic phase transition lowers the magnetostrictive constant. This ferromagnetic to paramagnetic transition is accompanied by large changes in the efficiency of electromagnetic ultrasound generation leading to the use of EMATs as a method of studying phase transitions in magnetic alloys [18].
doc_bio_tags: O O O O O O O O O O O O B I O O O O O B O O O O O B I I O O B I O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O B I O B I O O O O O O O O O O O O O O O O O O O B I I O O O O O B I I I O O O O O O O O O B I I O O O O O B O O O O B I I O B I O
extractive_keyphrases: electromagnetic ultrasound generation emats ferromagnetic oxide ferromagnetic to paramagnetic transition generation efficiency lorentz mechanism low carbon steel magnetic alloys magnetic field magnetic phase transition magnetostrictive mechanism steel studying phase transitions