Crossover of the dimensionality of3dspin fluctuations in LaCoPO

Abstract

dc magnetization and 31 P spin lattice relaxation rate in the polycrystalline sample of LaCoPO suggest a spin fluctuation dominated ferromagnetically ordered state. Moreover, NMR data clearly indicate a crossover from 2D to 3D spin fluctuations across TC. In contrast to isotropic hyperfine field, H hf at the 31 P site in LaFePO, H hf is anisotropic in LaCoPO. The data of spin lattice relaxation rate also exhibit anisotropic spin fluctuation. The anisotropy vanishes near TC.

Effect of Co-doping on the resistivity and thermopower of SmFe1-xCoxAsO (0.0≤x≤0.3)

“…Later on, search for superconductivity started in similar compounds with complete substitution of Fe with other 3d metals such as Co. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Contrarily, the magnetic properties, including itinerant ferromagnetism 17,26,27 and interacting RE 4f and Co 3d moments [28][29][30][31][32] have been studied recently albeit the iso-structural RECoAsO compounds do not superconduct.…”

Electron spin dynamics in grain-aligned LaCoPO: An itinerant ferromagnet

“…The T dependence of 139 La 1/T 1 T in LaCoPO shows the existence of non-negligible 3D spin fluctuations in both the paramagnetic and the ordered state over and above the dominant 2D spin fluctuations in the paramagnetic phase, observed from the previous 31 P NMR relaxation data in the same oriented sample. 9 The origin of this 3D spin fluctuations could be due to the existence of non-zero inter layer exchange interaction between the Co-P planes, which is communicated through the La-O plane situated in between as shown in Fig.1. By applying the SCR theory of Moriya to the magnetization data of LaCoPO, we have also determined the different spin fluctuation parameters along with the same from La NMR relaxation data.…”

“…In the present paper, we report the results of 139 La NMR studies in a grain aligned sample of LaCoPO in which 31 P NMR 9,10 showed the presence of dominant ferromagnetic (FM) 2D spin fluctuations in the paramagnetic state.…”

“…8,9 Derivative of the M vs T curve provides an approximate value of T C to be 35 K (inset of Fig. 2).…”

“…8 shows the 31 P (1/T 1 T ) H c versus temperature curve both in the paramagnetic and the ordered state. 9 In this case, Eq. 12 fits well (using χ of a sample not containing nonmagnetic impurity) only in the magnetically ordered region (represented by the continuous line) and deviates significantly in the paramagnetic region.…”