2007 - Ronald Fisch, Structure Factor of the 3D Random Field XY Model[1]
It appears that at the phase transition $M^2$ jumps to zero discontinuously, with a latent heat which is probably subextensive.
2008 - Yilong Han et al, Geometric Frustration in Buckled Colloidal Monolayers[2]
Experiment and theory reveal single-particle dynamics governed by in-plane lattice distortions that partially relieve frustration and produce ground-states with zigzagging stripes and subextensive entropy, rather than the more random configurations and extensive entropy of the antiferromagnetic Ising model.
2009 - Inés Armendáriz et al, Zero Range Condensation at Criticality[3]
We study the onset of condensation, i.e. the behaviour of the maximum occupation number after adding a subextensive excess mass of particles at the critical density.