Studies on passivating oxides on liquid metals are challenging, in part, due to plasticity, entropic, and technological limitations. In alloys, compositional complexity in the passivating oxide(s) and underlying metal interface exacerbates these challenges. This nanoscale complexity, however, offers an opportunity to engineer the surface of the liquid metal under felicitous choice of processing conditions. We inferred that difference in reactivity, coupled with inherent interface ordering, presages exploitable order and selectivity to autonomously present compositionally biased oxides on the surface of these metals. Besides compositional differences, sequential release of biased (enriched) components, via fractal‐like paths, allows for patterned layered surface structures. We, therefore, present a simple thermal‐oxidative compositional inversion (TOCI) method to introduce fractal‐like structures on the surface of these metals in a controlled (tier, composition, and structure) manner by exploiting underlying stochastic fracturing process. Using a ternary alloy, a three‐tiered (in structure and composition) surface structure is demonstrated.

Chameleon Metals. Metal passivating oxide layers are complex pseudo‐equilibrium systems with a plethora of undiscovered features. In their Research Article on page 352, M. Thuo et al. exploit the complexity of such a thin oxide layer to engineer surface design and structure, resulting in the formation of compositionally inverted surface features and nanoscale fractal‐like designs.

This paper reviews the ferromagnetic hysteresis, magnetomechanical and Barkhausen properties of magnetic materials and presents an integrated model to describe these effects and the underlying mechanisms that cause these effects. Hysteretic properties of ferromagnets such as permeability, coercivity, remanence and hysteresis loss are known to be sensitive to external factors including applied stress, temperature and heat treatment, and internal factors like residual strain, microstructure, grain size, and anisotropy and the presence of precipitates of a second phase, such as iron carbide in steels. It thus becomes imperative to characterize the effect of these factors on the hysteresis parameters. Currently, several models such as Preisach, Stoner-Wohlfarth and Jiles-Atherton are used to describe the magnetic hysteresis of ferromagnetic materials. We review here the quasistatic Jiles-Atherton hysteresis model which describes hysteresis in terms of domain wall motion enabling a connection to be made to the physical response of the magnetic material. This model has been extended to include the magnetomechanical effect and the Barkhausen effect in ferromagnetic materials. Theoretical work presented here provides a conceptual framework linking together these magnetic property measurements with model parameters and to the structure of the material.

Studies on passivating oxides on liquid metals are challenging, in part, due to plasticity, entropic, and technological limitations. In alloys, compositional complexity in the passivating oxide(s) and underlying metal interface exacerbates these challenges. This nanoscale complexity, however, offers an opportunity to engineer the surface of the liquid metal under felicitous choice of processing conditions. We inferred that difference in reactivity, coupled with inherent interface ordering, presages exploitable order and selectivity to autonomously present compositionally biased oxides on the surface of these metals. Besides compositional differences, sequential release of biased (enriched) components, via fractal‐like paths, allows for patterned layered surface structures. We, therefore, present a simple thermal‐oxidative compositional inversion (TOCI) method to introduce fractal‐like structures on the surface of these metals in a controlled (tier, composition, and structure) manner by exploiting underlying stochastic fracturing process. Using a ternary alloy, a three‐tiered (in structure and composition) surface structure is demonstrated.

In this work, an investigation of the effect of mechanical preloads on the hysteresis loop of composite soft magnetorheological elastomer (MRE) was carried out. MRE is a “smart” composite material that consists of magnetically permeable particles in a non-magnetic polymeric elastomer. When subjected to an external magnetic field, a large deformational change occurs in the mechanical properties of these materials. Due to their coupled magnetomechanical response, these materials have been found suitable for various engineering applications. Inspired by experimental work, we present a model of the effect of mechanical preloads on the magnetization response of MRE based on a general continuum formulation. Using the Jiles - Atherton (JA) model parameters derived from the fitting of experimental measurement, the hysteresis loop of isotropic MRE was numerically resolved, which was then coupled to mechanical fields based on an energetically constitutive model valid for finitely strained MREs. Simulation analysis is performed for uniaxial stresses parallel to the direction of the applied magnetic field. For the applied tensile and compressive stresses, only a small change is observed in the hysteresis loop of these materials. Additionally, microscale modeling of the magnetization behavior of the isotropic MRE based on experimental results was performed. Considering the interaction between the magnetic particles, the magnetic and mechanical fields are resolved explicitly inside the composite material. A computational homogenization scheme was utilized to relate the microscopic behavior to the effective macroscopic properties of the MRE. In principle, the predicted effective magnetization behavior is observed to agree with the measured hysteresis loop of MRE materials.