Surreal digital illustration of hybrid ferromagnetic material exhibiting magneto-optical Kerr effect.

Unlocking Ferromagnetism: How Hybrid Materials Are Changing Magnetic Technology

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Reese Marlowe in Tech & Innovation June 2025 • 4 min read.

"Delve into the innovative realm of metal/oxide hybrid ferromagnets and their magneto-optical properties, revealing their potential to revolutionize magnetic data storage and sensor technology."


In the ever-evolving landscape of materials science, hybrid ferromagnetic materials are emerging as key players, particularly in the realm of magnetic data storage and sensing technologies. These materials, which combine metallic and oxide phases, exhibit unique magneto-optical properties that hold immense potential for revolutionizing various applications.

Magneto-optical Kerr effect (MOKE) is a powerful technique to analyze the magnetic properties of thin films. Unlike traditional methods like SQUID or VSM, MOKE is surface sensitive, making it ideal for separating surface and volume contributions in layered systems. While standard magnetometry measures the magnetic moment of the entire sample, MOKE’s signal remains consistent, even with minimal thickness—perfect for studying thin films without experimental artifacts or contamination.

However, MOKE isn't without its challenges. Obtaining quantitative magnetization values requires intricate analysis, and the curves produced reflect light interaction with the material, not a direct representation of magnetization. Analyzing composite materials with MOKE introduces complexity; each element's contribution hinges not only on its volume fraction and magnetic properties but also on its optical and magneto-optical constants. Thus, the resulting signals might not accurately represent the magnetic properties of the entire material.

Metal/Oxide Hybrids: A Complex Landscape

Surreal digital illustration of hybrid ferromagnetic material exhibiting magneto-optical Kerr effect.

A particularly intriguing scenario involves heterogeneous materials that contain both metallic and oxide ferromagnetic phases. These can manifest as multilayers, patterned media, or partially oxidized metallic films. In such cases, analyzing magnetic properties using MOKE becomes complex, and improper analysis can yield misleading results. To illustrate this challenge, let’s examine a study on iron-based films with varying oxidation levels, analyzed using both MOKE and standard magnetometry techniques like VSM and SQUID.

The process began with depositing a 60 nm thick iron film onto sodalime glass via e-beam evaporation. MOKE measurements were then conducted using a homemade setup in a longitudinal configuration (p-polarization). A solid-state laser diode, operating at 635 nm wavelength, was employed. The laser beam, modulated at 213 Hz by a mechanical chopper, was analyzed using a lock-in amplifier. To account for any fluctuations in the incident beam, it was split into two, allowing for real-time compensation.

Key challenges in analyzing hybrid ferromagnetic materials with MOKE:
  • Complexity in signal interpretation due to the different optical properties of metals and oxides.
  • Requirement for sophisticated numerical analysis to accurately estimate phase fractions.
  • Potential for misleading results if analysis is not carefully performed.
  • Dependence of signal on both magnetic and optical properties of the constituent materials.
Figure 1 displays the magnetization curves obtained from both MOKE and SQUID magnetometers immediately following deposition. The curves exhibit an almost square shape and share a coercivity of 42 Oe. For this pure metallic film, longitudinal MOKE provides information that accurately represents the entire system. In contrast, Figure 2 presents magnetization curves for a magnetite (Fe3O4) film on an Au substrate, measured using both MOKE and SQUID. Despite minor differences due to experimental factors, the curves display a similar profile, confirming that longitudinal MOKE offers reliable information about the magnetization curve of materials in the case of pure oxide ferromagnetic films.

Insights and Conclusion

The study underscores that MOKE magnetization curves of hybrid metal-oxide ferromagnetic materials do not directly reflect the contribution of each phase to the material's overall magnetization. However, through meticulous numerical analysis, these curves can provide a reliable estimation of the fraction of metal and oxide present in the sample. This refined approach promises to unlock new potentials in material design and application, impacting diverse fields from data storage to sensor technology. By combining advanced analytical techniques with innovative material synthesis, we move closer to harnessing the full capabilities of hybrid ferromagnets, paving the way for next-generation magnetic devices.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1063/1.4996779, Alternate LINK

Title: Note: On The Study Of Metal/Oxide Hybrid Ferromagnets With Magneto-Optical Techniques

Subject: Instrumentation

Journal: Review of Scientific Instruments

Publisher: AIP Publishing

Authors: V. Lopez-Dominguez, P. De La Presa, A. Hernando, M. A. García

Published: 2017-08-01

Everything You Need To Know

1

What makes hybrid ferromagnetic materials suitable for advanced applications?

Hybrid ferromagnetic materials combine metallic and oxide phases, giving them unique magneto-optical properties. This combination has the potential to revolutionize magnetic data storage and sensing technologies by allowing for advanced material design and application.

2

How does Magneto-optical Kerr effect (MOKE) work, and what are its limitations when analyzing magnetic properties?

Magneto-optical Kerr effect (MOKE) is a surface-sensitive technique used to analyze the magnetic properties of thin films. It is particularly useful for distinguishing between surface and volume contributions in layered systems. MOKE measures the interaction of light with the material to determine the magnetic properties. However, obtaining quantitative magnetization values from MOKE requires careful analysis, as the signal reflects light interaction rather than a direct measure of magnetization. Also MOKE measurements on composite materials require consideration of volume fraction, magnetic properties, optical properties and magneto-optical constants.

3

Why is analyzing hybrid ferromagnetic materials more complex using MOKE?

When analyzing metal/oxide hybrid ferromagnetic materials, interpreting MOKE signals becomes complex because metals and oxides have different optical properties. Accurate estimation of phase fractions requires sophisticated numerical analysis. The resulting MOKE signals depend on both the magnetic and optical properties of the constituent materials, so inaccurate analysis can lead to misleading results.

4

What specific experimental methods were used in the study to analyze iron-based films with varying oxidation levels?

The study used a 60 nm thick iron film deposited on sodalime glass via e-beam evaporation. MOKE measurements were then taken using a homemade setup in a longitudinal configuration (p-polarization) with a solid-state laser diode operating at 635 nm. The laser beam, modulated at 213 Hz by a mechanical chopper, was analyzed using a lock-in amplifier. A beam splitter compensated for any fluctuations in the incident beam. Magnetization curves were also obtained using SQUID magnetometers for comparison.

5

In what ways can Magneto-optical Kerr effect (MOKE) be useful in estimating material composition, and what are its implications for future applications?

MOKE magnetization curves for hybrid metal-oxide ferromagnetic materials do not directly show each phase's contribution to the material's overall magnetization. However, with meticulous numerical analysis, MOKE curves can reliably estimate the fractions of metal and oxide present. This approach has the potential to unlock new possibilities in material design and application, which could impact fields such as data storage and sensor technology.

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