Critical exponents and scaling invariance in the absence of a critical point
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Date
2016Author
Saratz, Niculin
Zanin, Danilo Andrea
Ramsperger, Urs
Cannas, Sergio Alejandro
Pescia, Danilo
Vindigni, Alessandro
ORCID
https://orcid.org/0000-0002-7749-4104https://orcid.org/0000-0003-4424-2418
https://orcid.org/0000-0001-7331-3532
https://orcid.org/0000-0001-7436-418X
https://orcid.org/0000-0003-1941-5989
Metadata
Show full item recordAbstract
The paramagnetic-to-ferromagnetic phase transition is classified as a critical phenomenon due to the power-law behaviour shown by thermodynamic observables when the Curie point is approached. Here we report the observation of such a behaviour over extraordinarily many decades of suitable scaling variables in ultrathin Fe films, for certain ranges of temperature T and applied field B. This despite the fact that the underlying critical point is practically unreachable because protected by a phase with a modulated domain structure, induced by the dipole–dipole interaction. The modulated structure has a well-defined spatial period and is realized in a portion of the (T, B) plane that extends above the putative critical temperature,
where thermodynamic quantities do not display any singularity. Our results imply that scaling
behaviour of macroscopic observables is compatible with an avoided critical point.