Field-induced phase transitions in ferro-antiferromagnetic diblock copolymers
Abstract
We study the equilibrium properties of a model of magnetic diblock copolymer where each monomer is decorated with an Ising-like spin. Spins interact ferromagnetically within each block and antiferromagnetically across blocks, generating frustration between magnetic ordering and spatial organization. By employing a mean-field approach and Monte Carlo simulations for self-avoiding walks on the cubic lattice, we investigate the system's response to an external magnetic field. We discover a rich phase diagram that includes: a swollen phase with both filaments magnetically disordered and spatially extended; a mixed compact phase characterized by a single globule in which the two filaments are strongly intertwined; a segregated compact phase composed of two globular, magnetically ordered, and spatially separated blocks. Further, if the magnitude of the intra-block ferromagnetic interaction differs between the two blocks, we observe a hybrid segregated (``tadpole'') phase where one extended block coexists with a collapsed one. Mean-field predictions are in quantitative agreement with Monte Carlo results for the location of the phase boundaries. These findings provide a minimal statistical-mechanical framework for field-controlled self-assembly of tunable patterns by magnetically heterogeneous polymers. They may also serve as a simple platform to investigate the coupling between internal epigenetic-like states and chromatin folding.
Keywords
Cite
@article{arxiv.2602.22382,
title = {Field-induced phase transitions in ferro-antiferromagnetic diblock copolymers},
author = {Alberto Raiola and Emanuele Locatelli and Davide Marenduzzo and Enzo Orlandini},
journal= {arXiv preprint arXiv:2602.22382},
year = {2026}
}
Comments
13 pages, 9 figure plus supplemental information 6 pages, 3 figures