Ferromagnetism at room temperature in ball-milled Al-1at.%Fe

Abstract

Iron nano particles have been embedded in an aluminium matrix through high energy ball milling. The Mössbauer spectrum of the as-milled sample at room temperature shows the presence of a magnetic hyperfine sextet, a paramagnetic singlet and a quadrupole doublet with relative areas of nearly 78, 16 and 6%, respectively. The value of the hyperfine field for the sextet corresponds to that of ⍺-Fe. The quadrupole component, which is indicative of formation of an Al-rich solid solution, is broad with a width of 0.73 mm/s indicating a distribution in the quadrupole fields. The value of the average splitting is 0.5mm/s and isomer shift (IS) equal to 0.49mm/s with respect to metallic iron. M-H measurements show that the unmilled system is non-magnetic while the milled system of 30 min is ferromagnetic and exhibits very soft magnetic properties. Unreacted Fe clusters embedded at the nano-crystalline Al grain boundaries seem to be responsible for the observed net magnetic moment.