Fragility in a macroscopic model of a glass-forming liquid based on a nonvibrating granular system under a time-dependent magnetic field

We study the glass transition in a nonvibrating granular system composed of magnetic steel pellets under a variable magnetic field at a fixed particle concentration. The applied magnetic field is a superposition of a constant component and a sinusoidal component and is given by B=B_c+Bosen(2πft), where B_c is a constant magnetic field during an experiment, and can vary between 0 and 33 Gauss, B_o is the amplitude of the sinusoidal magnetic field which remains constant at 66 Gauss, and f is the oscillation frequency that takes the value of 9.25 Hz. It is observed that the fragility index changes if the B_c field changes. As the constant field increases, the system goes from a fragile to a strong glass-forming liquid behavior.