Experimental Study of Disorder-influenced First-Order Transitions in Vortex Matter and in Magnetic Systems

First-order transitions are frequently characterised by hysteresis as the control variable (which may be temperature T, or pressure P, or magnetic field H) is varied across the transition value T C (or P C , or H C ). This arises due to supercooling/superheating, with the existence of metastable states giving rise to hysteresis in physical properties. We shall present some of our recent studies on metastable states formed across a first-order transition in vortex matter, and also across a first-order magnetic transition. We shall discuss how quenched-in static disorder influences the nature of this transition process, and highlight the generality of such phenomena in other areas of condensed matter physics.