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Nanomaterials 2018, 8(4), 241; doi:10.3390/nano8040241

Structure and Magnetism of Mn5Ge3 Nanoparticles

1
Department of Physics and Astronomy, University of Delaware, Newark, DE 19711, USA
2
Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588, USA
3
Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
*
Author to whom correspondence should be addressed.
Received: 10 March 2018 / Revised: 10 April 2018 / Accepted: 12 April 2018 / Published: 15 April 2018
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Abstract

In this work, we investigated the magnetic and structural properties of isolated Mn5Ge3 nanoparticles prepared by the cluster-beam deposition technique. Particles with sizes between 7.2 and 12.6 nm were produced by varying the argon pressure and power in the cluster gun. X-ray diffraction (XRD)and selected area diffraction (SAD) measurements show that the nanoparticles crystallize in the hexagonal Mn5Si3-type crystal structure, which is also the structure of bulk Mn5Ge3. The temperature dependence of the magnetization shows that the as-made particles are ferromagnetic at room temperature and have slightly different Curie temperatures. Hysteresis-loop measurements show that the saturation magnetization of the nanoparticles increases significantly with particle size, varying from 31 kA/m to 172 kA/m when the particle size increases from 7.2 to 12.6 nm. The magnetocrystalline anisotropy constant K at 50 K, determined by fitting the high-field magnetization data to the law of approach to saturation, also increases with particle size, from 0.4 × 105 J/m3 to 2.9 × 105 J/m3 for the respective sizes. This trend is mirrored by the coercivity at 50 K, which increases from 0.04 T to 0.13 T. A possible explanation for the magnetization trend is a radial Ge concentration gradient. View Full-Text
Keywords: magnetic nanoparticles; cluster deposition; magnetization magnetic nanoparticles; cluster deposition; magnetization
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Tosun, O.; Salehi-Fashami, M.; Balasubramanian, B.; Skomski, R.; Sellmyer, D.J.; Hadjipanayis, G.C. Structure and Magnetism of Mn5Ge3 Nanoparticles. Nanomaterials 2018, 8, 241.

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