Experimental evidence for the formation of CoFe2C phase with colossal magnetocrystalline-anisotropy

Journal Article · Mon May 25 00:00:00 EDT 2015 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4921789· OSTI ID:1211351

El-Gendy, AA; Bertino, M; Clifford, D; Qian, MC; Khanna, SN; Carpenter, EE

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe2C) of nanoparticles. Structural characterization of the CoFe2C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, TB, of 790K for particles with a domain size as small as 5 +/- 1 nm. The particles have magnetocrystalline anisotropy of 4.662 +/- 10 6 J/m(3), which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe2C nanoparticles have huge potential for enhanced magnetic data storage devices. (C) 2015 AIP Publishing LLC.

• Sponsoring Organization: USDOE Advanced Research Projects Agency - Energy (ARPA-E)
• DOE Contract Number: 1574-1674
• OSTI ID: 1211351
• Journal Information: Applied Physics Letters, Vol. 106, Issue 21; ISSN 0003-6951
• Country of Publication: United States
• Language: English