Identification of stable alloy with giant magnetization via machine learning based autonomous materials search

Discovery of new magnets with high magnetization has always been important in human history because it has given birth to powerful motors and memory devices. Currently, the binary alloy Fe 3 Co 1 exhibits the largest magnetization of any stable alloys explained by the Slater-Pauling rule. A multi-element alloy system has been expected to include an alloy with magnetization beyond that of Fe 3 Co 1 , but it has been difficult to identify appropriate elements and compositions because of combinatorial explosion in the multi-element system. In this work, we found a new alloy with giant magnetization beyond that of Fe 3 Co 1 via an autonomous materials search system combining machine learning and ab-initio calculation. After autonomous/automated exploration in the large material space of multi-element alloy for six weeks, the system unexpectedly indicated that Ir and/or Pt impurities would enhance the magnetization of FeCo alloys. To confirm this experimentally, we comprehensively synthesized Fe x Co y Ir 1-x-y and Fe x Co y Pt 1-x-y alloys and found that some of them have magnetization beyond that of Fe 3 Co 1 .