Magnetometry of single ferromagnetic nanoparticles using magneto-optical indicator films with spatial amplification

Journal Article · Mon Mar 16 00:00:00 EDT 2015 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4916205· OSTI ID:22395757

Hangarter, Carlos ^[1]; Stavis, Samuel M.; Unguris, John ^[2]

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1. Materials Science and Engineering Division, Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
2. Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

We present a magneto-optical technique to spatially amplify and image fringe fields from single ferromagnetic nanorods. The fringe fields nucleate magnetic domains in a low-coercivity, perpendicularly magnetized indicator film, which are expanded by an applied out-of-plane field from the nanoscale to the microscale for measurement with polar Kerr microscopy. The nucleation location and therefore magnetic orientation of the sample nanorod are detected as spatially dependent field biases in locally measured hysteresis loops of the indicator film. We first discuss our method to fabricate the high-sensitivity indicator film with low energy argon ion irradiation. We then present a map of the amplified signal produced from a single nanorod as measured by the indicator film and compare it with a simultaneously obtained, unamplified fringe field map. The comparison demonstrates the advantage of the amplification mechanism and the capability of the technique to be performed with single-spot magneto-optical Kerr effect magnetometers. Our signal-to-noise ratio determines a minimum measureable particle diameter of tens of nanometers for typical transition metals. We finally use our method to obtain hysteresis loops from multiple nanorods in parallel. Our technique is unperturbed by applied in-plane fields for magnetic manipulation of nanoparticles, is robust against many common noise sources, and is applicable in a variety of test environments. We conclude with a discussion of the future optimization and application of our indicator film technique.

• OSTI ID: 22395757
• Journal Information: Applied Physics Letters, Vol. 106, Issue 11; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMPLIFICATION
ARGON IONS
COERCIVE FORCE
COMPARATIVE EVALUATIONS
FERROMAGNETIC MATERIALS
FERROMAGNETISM
FILMS
HYSTERESIS
IRRADIATION
KERR EFFECT
MAGNETO-OPTICAL EFFECTS
MICROSCOPY
NANOPARTICLES
NANOSTRUCTURES
NUCLEATION
SIGNAL-TO-NOISE RATIO
TRANSITION ELEMENTS