Criticality of Interface Depinning and Origin of "Bump" in the Avalanche Distribution.

The depinning transition critical point is manifested as power-law distributed avalanches exhibited by slowly driven elastic interfaces in quenched random media. Here we show that since avalanches with different starting heights relative to the mean interface height or different initial local interface curvatures experience different excess driving forces due to elasticity, avalanches close to the "global" critical point of non-mean-field systems can be separated into populations of subcritical, critical, and supercritical ones. The asymmetric interface height distribution results in an excess of supercritical avalanches, manifested as a "bump" in the avalanche size distribution cutoff.

Magnetic domain wall dynamics studied by in-situ Lorentz microscopy with aid of custom-made Hall-effect sensor holder.

We built a custom-made holder with a Hall-effect sensor to measure the single point magnetic flux density inside a transmission electron microscope (TEM, JEM-F200, JEOL). The measurement point is at the same place as the sample inside the TEM. We utilized information collected with the Hall-effect sensor holder to study magnetic domain wall (DW) dynamics by in-situ Lorentz microscopy.

Barkhausen noise in disordered striplike ferromagnets: Experiment versus simulations.

In this work, we present a systematic comparison of the results obtained from the low-frequency Barkhausen noise recordings in nanocrystalline samples with those from the numerical simulations of the random-field Ising model systems. We performed measurements at room temperature on a field-driven metallic glass stripe made of VITROPERM 800 R, a nanocrystalline iron-based material with an excellent combination of soft and magnetic properties, making it a cutting-edge material for a wide range of applications. Given that the Barkhausen noise emissions emerging along a hysteresis curve are stochastic and depend in general on a variety of factors (such as distribution of disorder due to impurities or defects, varied size of crystal grains, type of domain structure, driving rate of the external magnetic field, sample shape and temperature, etc.

Reversible-to-irreversible transition of colloidal polycrystals under cyclic athermal quasistatic deformation.

Cyclic loading on granular packings and amorphous media exhibits a transition from reversible elastic behavior to irreversible plasticity. The present study compares the irreversibility transition and microscopic details of colloidal polycrystals under oscillatory tensile-compressive and shear strain. Under both modes, the systems exhibit a reversible to irreversible transition.

Predicting elastic and plastic properties of small iron polycrystals by machine learning.

Deformation of crystalline materials is an interesting example of complex system behaviour. Small samples typically exhibit a stochastic-like, irregular response to externally applied stresses, manifested as significant sample-to-sample variation in their mechanical properties. In this work we study the predictability of the sample-dependent shear moduli and yield stresses of a large set of small cube-shaped iron polycrystals generated by Voronoi tessellation, by combining molecular dynamics simulations and machine learning.