The ferromagnetic and antiferromagnetic phases in anion deficient La0.5−xPrxBa0.5CoO3−δ cobaltites

Abstract

Creeping of minor hysteresis loops in Co thin films J. Appl. Phys. 112, 063919 (2012) Invariance of the magnetization axis under spin reorientation transitions in polycrystalline magnets of Nd2Fe14B J. Appl. Phys. 112, 063918 (2012) Procedure for numerical integration of the magnetocaloric effect J. Appl. Phys. 112, 063920 (2012) Vortex dynamics in triangular-shaped confining potentialsNeutron powder diffraction studies of crystal and magnetic structures, magnetization and magnetotransport measurements have been performed for La 0.5Àx Pr x Ba 0.5 CoO 3Àd (x 0:375, d < 0:25) cobaltites. It has been found that the compositions (0 x 0:35) are cubic (Pm3m) whereas x ¼ 0:375 one is tetragonal (P4/mmm) due to an ordering of rare-earth and barium ions, while the oxygen vacancies are disordered. The oxygen content decrease leads to transformation of the magnetic structure from ferromagnetic to the G-type antiferromagnetic one through the mixed two-phase magnetic state. The compositions with antiferromagnetic component show structural phase separation, strong increase of the unit cell volume upon cooling, and anomalous magnetization behavior. It is suggested that these phenomena are associated with stabilization of Co 3þ ions in high/low spin state at low temperature. The high/low spin state corresponds antiferromagnetic phase, whereas in the ferromagnetic one, the Co 3þ and Co 4þ ions adopt intermediate spin state. V C 2012 American Institute of Physics. [http://dx.

Possible surface antiferromagnetism and no evidence for intergranular tunneling magnetoresistance in La0.5Sr0.5CoO3–δ cobaltites

“…6) can be ascribed to field induced spin state transition from antiferromagnetic into ferromagnetic phase. 7,8 This transition was suggested to occur via structural distortion induced by magnetic field. 7,8 The structural distortion stabilizes the IS state and destabilizes both HS and LS states.…”

“…The oxygen deficit stabilizes an antiferromagnetic phase in both La 0.5 Ba 0.5 CoO 3-d and La 0.5 Sr 0.5 CoO 3-d series. [6][7][8] It was suggested that the magnetic moment of 1.5 l B in metallic La 0.5 Sr 0.5 CoO 3 can be rationalized with an intermediate-spin model having localized t 5 2g configurations on each cobalt ion and an narrow itinerant r* band containing 0.5 electrons per Co atom magnetized ferromagnetically. 9 However, according to Refs.…”

Cr enhanced ferromagnetism in La0.5Ba0.5CoO3 due to possible double-exchange interaction

“…Dry pure La 2 O 3 , BaCO 3 , Co 3 O 4 , CuO, ZnO, Cr 2 O 3 , Ni 2 O 3 , TiO 2 and RuO 2 powders were well mixed in the stoichiometric amounts and initially decarbonated in the air at 1170 K for 20 h. After regrinding, the samples were fired in the air at 1470 K for 15 h and slowly cooled for several times [4,23]. The cooling rate is 30 K/h.…”

“…The origin of the ferromagnetic state in metallic cobaltites has been a subject of discussion for a long time. One knows that cobaltites are extremely sensitive to order-disorder, doping, temperature, and crystal structure [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. The substitution of other ions for Co ions could directly modify the magnetic ordering and facilitate understanding the nature of the ferromagnetic state as well as clarifying the spin state of Co ions.…”

Исследование спинового перехода в монокристалле LaCoO-=SUB=-3-=/SUB=- методом рентгеновского магнитного кругового дихроизма на K- и L-=SUB=-2,3-=/SUB=--краях кобальта

“…Следует отметить, что наши XMCD результаты на L 2,3 -краях хорошо согласуются и дополняют данные, ранее полученные методом XMCD в [13], а также данные представленые в работе по неупругому нейтронному рассеянию [11], нейтронной дифракции и EXAFS [20][21][22][23].…”