Spin reorientation temperature of ultrafine and nanostructured Nd2Fe14B particles obtained by surfactant-assisted ball milling

• Published in: Physics letters. A Vol. 385; p. 126954
• Main Authors: Pal, Santosh K., Müller, K.-H., Schultz, L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 07.01.2021
• Subjects: Ball milling; Exchange coupling; HDDR; Nd2Fe14B; Spin reorientation; Ball milling; Nd2Fe14B; Spin reorientation; HDDR; Exchange coupling
• ISSN: 0375-9601; 1873-2429
• DOI: 10.1016/j.physleta.2020.126954

•Microstructural parameters significantly influence TSR in Nd2Fe14B.•TSR increases for ultrafine single crystalline Nd2Fe14B particles.•Nanostructured polycrystalline Nd2Fe14B nanoflakes show significantly low TSR.•Intergrain magnetic exchange coupling controls the TSR in ultrafine Nd2Fe14B particles. Spin reorientation temperature (TSR) of sintered Nd2Fe14B ingots, hydrogenation-disproportionation-desorption-recombination (HDDR) processed Nd2Fe14B powder and surfactant-assisted ball-milled ultrafine nanostructured Nd2Fe14B particles has been determined. TSR value was found to decrease from 135 K for sintered Nd2Fe14B ingot to 129 K for HDDR processed Nd2Fe14B particles of 50-200 μm size composed of ∼300 nm grains. Interestingly, TSR value was increased after surfactant-assisted (SA) ball milling of HDDR powder reaching 134 K for 1-2 μm particles and 136 K for ∼300 nm isolated single-crystalline particles. Transformation of single-crystalline particles to polycrystalline flakes after intense SA-ball milling resulted in a decrease of the TSR to a value of 128 K. A detailed crystallographic, microstructural, and magnetic investigations have been performed and the possible reasons for the variation of TSR value have been discussed.