Abstract
Metamagnetic FeRh has been the focus of numerous studies for its highly unique antiferromagnetic (AF) to ferromagnetic (FM) metamagnetic transition. While this phase transition usually occurs above room temperature (often Tc > 400 K), both ion irradiation and strained epitaxial growth have been used to bring it to applicable temperatures. Nevertheless, cross sample variability is pervasive in these studies. Here we explore the optical and magnetic properties of 35 nm thick FeRh grown by magnetron sputter deposition simultaneously on two different single crystal substrates: epitaxially on MgO (001) and highly strained with large lattice mismatch on Al2O3 (1000). We then irradiate the epitaxial film with 5 keV N+ ions to introduce disorder (and to a lesser extent, modify chemical composition) without effecting the surface morphology. We find that the phase-transitional properties of both films are strikingly different due to the large lattice mismatch, despite being grown in tandem with nominally identical growth conditions including Fe/Rh stoichiometry, pressure, and temperature. We observe that N+ implantation lowers Tc by ~60 K, yielding a sample with nominally the same transition temperature as the non-epitaxial film on sapphire, yet with a significantly increased magnetic moment, a larger magnetization change and a more abrupt transition profile. We attribute these differences to the Volmer-Weber type growth mode induced by the sapphire substrate and the resulting rougher surface morphology.
Highlights
Interest in phase transitional materials has grown over recent years
This is especially interesting since devices which seek to harness the metamagnetic transition in FeRh will operate around room temperature and a magnetic hysteresis provides an inherent memory effect [33]
We have investigated the difference between controlling the metamagnetic tranHere we have investigated the difference between controlling the metamagnetic transition
Summary
Interest in phase transitional materials has grown over recent years. A significant driver for this change has been an increased need for more robust, lower power and higher speed memory electronics [1,2]. The memristive capabilities of phase change materials such as the metal insulator transitional VO2 and V2 O3 are prime candidates for this generation [6,7,8]. A common observation among these studies is the major role strain plays in the metamagnetic transition This strain-led variation of the exchange integral leads to substantial variations in the transition temperature. SQUID magnetometry, the magneto-optic Kerr effect (MOKE), and optical reflectance By growing on both substrates in tandem we have shown for the first time the clear differences between morphological versus irradiative control of the metamagnetic transition in FeRh without questions of cross sample thickness and compositional variability
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