Magnetic and Structural Properties of Iron Alloys

Synopsis

The structural and magnetic properties of sputter-deposited Fe_100−xRu_x films were studied for x ≤ 50. The crystal structure of Fe_100−xRu_x is shown to be predominantly body-centered cubic for x < 13 and to undergo a gradual transition to hexagonal close-packed in the concentration range 13 ≲ x ≲ 20. Magnetic measurements indicate that the addition of Ru induces a noncollinear magnetic order in the body-centered cubic FeRu alloys, while the hexagonal close-packed FeRu alloys exhibit paramagnetic behavior. Increasing the Ru concentration in body-centered cubic FeRu alloys decreases the size of magnetic domains, approaching the size of magnetic grains. A simple atomistic model was used to show that the competition antiferromagnetic coupling of Fe atoms across Ru atoms and ferromagnetic coupling between neighbouring Fe atoms can be responsible for inducing noncollinear order in the FeRu cubic structures. Magnetic multilayer structures used in thin-film magnetic devices make extensive use of both Fe and Ru layers. Our results reveal that the presence of even a small amount of Ru in Fe influences the magnetic order of Fe, potentially negatively impacting device performance.

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