Comment on Exchange bias in the layered cobaltite Sr1.5Pr0.5CoO4 [J. Appl. Phys. 104, 023914 (2008)]

Ang [J. Appl. Phys. 104, 023914 (2008)] recently reported magnetization hysteresis loops shifted along both field and magnetization axes of layered cobaltites. The authors claimed that these shifts are characteristics of the exchange-bias phenomenon associated with coupling between ferromagnetic and spin-glass regions. The present comment affirms that their work shows no proofs supporting the observation of exchange bias since, due to lack of magnetic reversibility at high magnetic fields, all hysteresis loops displaced from the origin are actually minor loops naturally shifted along both axes.