Comment on "Formation of magnetic glass in calcium doped YBaCo₂O_(5.5) cobaltites" [arXiv:1106.6253]

A recent paper from Raveau's group (arXiv:1106.6253) has shown the existence of a glass-like arrested state in two calcium-doped cobaltites, which consists of coexisting ferromagnetic and antiferromagnetic phase fractions, resulting from arrest of kinetics at low temperature,. They use the "cooling and heating in unequal magnetic field (CHUF)" measurement protocol to show devitrification of the arrested state. They use the same section title, protocol name, and acronym as in the paper (arXiv:0805.1514) where the protocol was presented, justified, and exploited. They nowhere refer to that paper, or to its journal counterpart. We put the development of this CHUF protocol in perspective, bringing out that it was conceived for broadened first order transitions where the kinetics of the transformation gets hindered. We also point out its applicability in view of our various subsequent works (arXiv:0911.4552, arXiv:1003.4400 and their journal counterparts) further exploiting this protocol. The paper being commented on is also silent about these latter papers (or their journal counterparts) even though the use of this protocol is highlighted in these in the abstract itself.