[Paper Review] Disorder-induced significant enhancement in magnetization of ball-milled Fe2CrGa alloy

Hongguo Zhang, C. Z. Zhang+7 more|arXiv (Cornell University)|Mar 20, 2013

Magnetic Properties of Alloys23 references19 citations

TL;DR

This study demonstrates that ball-milling Fe2CrGa alloy induces atomic disorder that significantly enhances its magnetization to 3.2–3.9 μB and increases the Curie temperature by ~200 K compared to arc-melted samples. First-principles calculations and experiments confirm that magnetic interactions drive the stabilization of a disordered Hg2CuTi-based structure, defying conventional empirical rules.

ABSTRACT

A new disordered atom configuration in Fe2CrGa alloy has been created by ball-milling method. This leads to a significant enhancement of the magnetic moment up to 3.2~3.9 μB and an increase of Curie temperature by about 200 K, compared with the arc-melt samples. Combination of first-principles calculations and experimental results reveals that Fe2CrGa alloy should crystallize in Hg2CuTi based structure with different atomic disorders for the samples prepared by different methods. It is addressed that magnetic interactions play a crucial role for the system to adopt such an atomic configuration which disobeys the empirical rule.

Motivation & Objective

• To investigate the effects of mechanical milling on the magnetic and structural properties of Fe2CrGa Heusler alloy.
• To understand the origin of enhanced magnetization and Curie temperature in ball-milled Fe2CrGa compared to conventional arc-melted samples.
• To determine whether atomic disorder can stabilize a non-stoichiometric, disordered Hg2CuTi-based structure in Fe2CrGa and how magnetic interactions influence this configuration.
• To challenge the empirical rules governing Heusler alloy stability by demonstrating that magnetic interactions can favor disordered configurations.

Proposed method

• Ball-milling was used to induce atomic-scale disorder in Fe2CrGa alloy, altering its crystal structure and magnetic properties.
• X-ray diffraction and electron microscopy were employed to characterize the disordered atomic configuration and structural changes.
• First-principles density functional theory (DFT) calculations were performed to analyze the electronic structure and magnetic interactions in the disordered phase.
• Magnetic measurements, including M-H hysteresis and temperature-dependent magnetization, were used to quantify the enhanced magnetic moment and Curie temperature.
• Comparative analysis between ball-milled and arc-melted samples was conducted to isolate the effects of disorder on magnetic behavior.

Experimental results

Research questions

• RQ1 How does ball-milling affect the atomic structure and magnetic properties of Fe2CrGa Heusler alloy?
• RQ2 What is the role of magnetic interactions in stabilizing a disordered Hg2CuTi-based structure in Fe2CrGa?
• RQ3 Why does the disordered phase exhibit a higher Curie temperature and larger magnetic moment than the ordered arc-melted phase?
• RQ4 To what extent does the observed enhancement violate empirical rules for Heusler alloy stability?

Key findings

• Ball-milled Fe2CrGa exhibits a magnetic moment of 3.2–3.9 μB, significantly higher than that of arc-melted samples.
• The Curie temperature of ball-milled Fe2CrGa increases by approximately 200 K compared to the arc-melted reference.
• First-principles calculations confirm that the disordered Hg2CuTi-based structure is energetically stabilized by strong magnetic interactions.
• The observed atomic disorder defies conventional empirical rules for Heusler alloy formation, indicating that magnetic interactions dominate structural stabilization in this system.