Magnetic hardness features and loop shift in nanostructured CuO

Abstract

Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO3 incorporated in (BiFeO3)0.50 (Co0.4Zn0.4Cu0.2 Fe2O4)0.5 nanocomposite AIP Advances 4, 037112 (2014); 10.1063/1.4869077 Core/shell magnetism in NiO nanoparticles J. Appl. Phys. 114, 083906 (2013); 10.1063/1.4819807 Structural and room-temperature ferromagnetic properties of Fe-doped CuO nanocrystalsNanostructures of cupric oxide (CuO) obtained by ball milling show drastic changes in its magnetic behavior that cannot be only associated to a size effect. While sample of average size D ¼ 29 nm presents a magnetic behavior that resembles that of bulk material with a N eel temperature of 195 K, another sample with D ¼ 24 nm displays a departure from the magnetic features typical of bulk CuO and has magnetic hardness characteristics at low temperatures. Both samples show irreversibility above room temperature and shifts in their hysteresis loops along magnetization and field axis when field cooled in a H FC ¼ 50 kOe to 10 K. At this temperature, an apparent exchange bias like field, "H EB ", 0.17 and 1.06 kOe were estimated for 29 and 24 nm CuO samples, respectively. Magnetic behavior differences observed in samples subjected to distinct milling times are explained as due to a proposed model for milled CuO consisting of a multilayer configuration where interfaces comprise uneven structural disorder and oxygen deficiencies, which generate a peculiar antiferromagnetic/ferromagnetic interface configuration. V C 2012 American Institute of Physics. [http://dx.

Pulsed Field-Induced Magnetization Switching in Antiferromagnetic Ferrihydrite Nanoparticles

“…On the other hand, the magnetic moment of an AFM particle can be exchange-coupled with the AFM core, which can give rise to an additional anisotropy. This mechanism possibly manifests itself in the shift of the magnetic hysteresis loop of AFM particles after their cooling in external field from a temperature over T B [6][7][8][9][10][11][12][13]. In addition, it is worth noting that the magnetization curve of an ensemble of AF nanoparticles is, in the first approximation (with disregard of the exchange coupling between μ p and the AFM core), a superposition of the contributions of the magnetic moments of particles and the characteristic field-linear magnetic response of the antiferromagnetically ordered core [1,2,[14][15][16][17][18][19][20][21].…”

Hysteresis loops in CuO

“…Para ajustar la componente ferromagnética se utilizó la función propuesta por Stearns y Cheng [16]: En estudios previos hemos demostrado que muestras de CuO obtenidas por MM durante diferentes tiempos [12,13], tm, presentan lazos de histéresis con valores de coercividad y remanencia que aumentan con tm, asignado este resultado a la influencia del tamaño de las zonas de difracción coherente y a la anisotropía de las microtensiones. Otros autores atribuyen esta clase de respuesta sólo a la reducción del tamaño [13], que genera efectos de borde dando lugar a dos órdenes magnéticos diferentes. Recientemente Gao et al [17], entre otros, atribuyen los lazos de histéresis a la presencia de vacancias de oxígeno que inducen coexistencia de iones Cu 1+ y Cu 2+ , mientras que Vila et al lo atribuyen, en acuerdo con Xiao et al [6], a la anisotropía de forma.…”

“…En nuestro trabajo previo hemos observado FM a t.a. en nanoestruturas obtenidas por molienda mecánica de CuO comercial que hemos atribuido a anisotropía de las microtensiones [12,13]. En el presente trabajo se presentan los primeros resultados de una investigación tendiente a profundizar en el origen del ferromagnetismo que hemos observado a t.a.…”

Импульсное Перемагничивание Антиферромагнитных Наночастиц Ферригидрита

“…С другой стороны, магнитный момент AF-частички может быть обменно связан с AF-" ядром", и это может быть источником дополнительной анизотропии. Указанный механизм, возможно, проявляется в смещении петли магнитного гистерезиса AF-частиц после их охлаждения во внешнем поле от температуры, превышающей T B [6][7][8][9][10][11][12][13]. Отметим также, что кривая намагничивания ансамбля AF-наночастиц в первом приближении (без учета обменной связи µ p и AF-" ядра") является суперпозицией вкладов от магнитных моментов частиц и характерного, линейного по полю, магнитного отклика от AF-упорядоченного " ядра" [1,2,[14][15][16][17][18][19][20][21].…”