Search for ferromagnetism in Mn-doped lead halide perovskites

Lead halide perovskites are new key materials in various application areas such as high efficiency photovoltaics, lighting, and photodetectors. Doping with Mn, which is known to enhance the stability, has recently been reported to lead to ferromagnetism below 25 K in methylammonium lead iodide (MAPbI(3)) mediated by superexchange. Two most recent reports confirm ferromagnetism up to room temperature but mediated by double exchange between Mn2+ and Mn3+ ions. Here we investigate a wide concentration range of MAMn(x)Pb(1-x)I(3) and Mn-doped triple-cation thin films by soft X-ray absorption, X-ray magnetic circular dichroism, and quantum interference device magnetometry. The X-ray absorption lineshape shows clearly an almost pure Mn2+ configuration, confirmed by a sum-rule analysis of the dichroism spectra. A remanent magnetization is not observed down to 2 K. Curie-Weiss fits to the magnetization yield negative Curie temperatures. All data show consistently that significant double exchange and ferromagnetism do not occur. Our results show that Mn is not suitable for creating ferromagnetism in lead halide perovskites. There have been recent studies reporting that Mn-doped MAPBI(3) houses a ferromagnetic phase mediated by a double exchange mechanism. Here, however, using X-ray magnetic circular dichroism and magnetic susceptibility measurements, the authors uncover contradicting experimental evidence to indicate an absence of magnetic ordering in this material, suggesting that our understanding of Mn-doped lead halide perovskites may need reassessing.

Automated summary

Lead halide perovskites are new key materials with various applications. Recent reports suggest that doping with Mn can lead to ferromagnetism, but our study shows that significant double exchange and ferromagnetism do not occur in Mn-doped lead halide perovskite thin films. Our results indicate that Mn is not suitable for creating ferromagnetism in lead halide perovskites.