Who: Lorenzo Fallarino, Nanomagnetism group
Place: nanoGUNE online webinar
Date: Monday, 8 February 2021, 11:00
Tuning critical exponents via nano-scale materials design
Nanomagnetism Group, CIC nanoGUNE
While nano-scale materials design has been tremendously successful in creating optimized magnetic and spintronic properties, the ferromagnetic - paramagnetic phase transition was considered beyond the realm of such efforts. Due to the universality of phase transitions and associated quantities such as the critical exponent beta of the order parameter, nano-scale design details were regarded as irrelevant, which in turn severely limits materials design capabilities towards the onset of the ferromagnetic order. Here, we demonstrate that this universality assumption can be overcome by appropriate nano-scale materials design and that critical exponents can be tuned in an extremely wide parameter range. Our results reveal that graded magnetic materials, in which a depth dependent exchange coupling strength follows a V-shaped profile, exhibit critical scaling behaviour over many orders of magnitude, but with critical exponents that can be designed and controlled by their specific nano-scale structures. Specifically, we report the first experimental observation of M(T) following a power-law behaviour with a la carte tuneable critical exponents, opening an unexplored design route for any technology, whose performance is impacted by materials M(T) characteristics, since beta can now be accessed as a materials design parameter.
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