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oai:docta.ucm.es:20.500.14352/520962023-08-25T15:33:06Zcom_20.500.14352_14col_20.500.14352_15
Docta Complutense author Gorria, Pedro author Martínez Blanco, David author Blanco, Jesús A. author Pérez, María José author Hernando Grande, Antonio author Fernández Barquín, luis author Smith, Ronald I. 2023-06-20T12:39:32Z 2023-06-20T12:39:32Z 2005-07 1098-0121 10.1103/PhysRevB.72.014401 https://hdl.handle.net/20.500.14352/52096 http://dx.doi.org/10.1103/PhysRevB.72.014401 https://journals.aps.org Experimental results of magnetization and neutron diffraction in the temperature range 300-1100 K evidence an anomalous high-temperature irreversible magnetic behavior on metastable FeCu solid solutions. When the temperature is increased above 500 K, a segregation process takes place in the as-milled sample which gives rise to the appearance of Fe (bcc) and Cu (fcc) phases. Further heating shows that the magnetization at 850 K falls down due to the temperature dependence of the bcc-Fe magnetization and the onset of the alpha-gamma martensite transformation. The temperature of this martensite phase transition (1020 K) is more 100 K lower than that of pure alpha-Fe (1183 K). On cooling from high temperatures (1100 K), the magnetization does not appreciably increase its value until the temperature is lowered below 900 K, showing a broad hysteresis between the forward (warming) and the reverse (cooling) transformations. Apart of the above mentioned bcc-Fe and fcc-Cu phases, on cooling, a small amount of isolated gamma-Fe precipitates (approximate to 5%) is detected. Further heating above 600 K show a large magnetization enhancement, reaching a value 50% higher with respect to the value measured at room temperature. During cooling from 1100 K the maximum value of magnetization is not recovered. The origin of this anomalous high temperature magnetic behavior is explained on the basis of strong magnetovolume instabilities in gamma-Fe. Furthermore, the thermal expansion coefficient of the gamma-Fe precipitates (21-23x10(-6) K-1), obtained from the neutron-diffraction patterns, is in excellent agreement with that calculated theoretically (20-24x10(-6) K-1, along the studied temperature range 300-1100 K). This fact is a signature of an anti-Invar behavior in gamma-Fe precipitates that could explain this surprising magnetic response. eng High-temperature induced ferromagnetism on gamma-Fe precipitates in FeCu solid solutions journal article URL https://docta.ucm.es/bitstreams/abe3df32-1130-4b97-ae05-3d3de02d7019/download File MD5 19bc69a0ad66dc6970abbec3fabdf170 492343 application/pdf HernandoGrande 15 libre.pdf