Electron paramagnetic resonance of magnetoelectric Pb(Fe1∕2Nb1∕2)O3

Abstract

To check on the nature of the weak magnetic order in polycrystalline magnetoelectric Pb(Fe1∕2Nb1∕2)O3 the X-band, Q-band, and far infrared electron paramagnetic resonance (EPR) spectra have been measured between 4 and 600K and compared with magnetic susceptibility and magnetization data. The asymmetric line shapes can be simulated at higher temperature by thermally fluctuating superparamagnetic nanoclusters. The pronounced temperature dependence of the position of the spectra demonstrates the presence of an internal magnetic field which is small but nonzero even at room temperature, i.e., far above the antiferromagnetic transition. The electronic spin-spin exchange has been found to be in the terahertz range. The magnetization data reveal a weak ferromagnetism even above 300K and a break in the temperature dependence of susceptibility at the paramagnetic to ferromagnetic transition.

Room-temperature single phase multiferroic magnetoelectrics: Pb(Fe, M)x(Zr,Ti)(1−x)O3 [M = Ta, Nb]

“…0.06 emu g À1 , this is 7% of the maximum possible value for all Fe spins aligned at T ¼ 0 and is gives some estimate of the degree of spin clustering at room temperature, the values obtained are comparables to the values reported by R. Blinc et al for PFN ceramic multiferroic relaxor. 43 In Figure 4(b), we compare the remanent magnetization (M r ) and coercive magnetic field (H c ) obtained from M vs. H curve for PFN x -PZT 1Àx and PFT y -PZT 1Ày solid solution ceramic samples with x or y varying between 0.1 and 0.4. Similar trend for M r and H c was observed in both families, the higher magnetic properties were observed for x/y ¼ 0.2.…”

Symmetries and multiferroic properties of novel room-temperature magnetoelectrics: Lead iron tantalate – lead zirconate titanate (PFT/PZT)

“…These systems showed the good remanent magnetization (0.07 and 0.024 emu/g for x=0.3 and 0.4 respectively at room temperature) which is comparable to the known room temperature multiferroics including bismuth ferrite and other lead based multiferroic relaxors. [37][38][39][40][41][42] The room temperature magnetization value of 0.4 Bohr magnetons per Fe +3 spin using known density of 7.5 g/cc and cell volume of 64 x 10 -18 cm -3 is quite reasonable. This magnetization is equivalent to about 7 % of the saturation value of 5.9 μ B .…”

“…R. Blinc et al has carried out the electron paramagnetic resonance (EPR) experiment on PFN ceramic and explains the presence of weak magnetization above Neel temperature in context of super paramagnetic cluster model. 40 The explanation of observed weak magnetization in M vs H curve or ZFC-FC data in PFN, PFT, or PFW (same class) materials was first given by Prof. Smolenskii, they explained on the basis of super-exchange interaction at B-site octahedral and also spin canting. The existence of magnetization above the Neel temperature in sol-gel prepared PFN ceramic had explained on the basis of spins canting and super-paramagnetic ions cluster.…”

“…A sharp increase in magnetization was observed below 50 K. Neels temperature (T N ) related to the original PFT was not observed in ZFC and FC magnetization curve suggests the existence of super-antiferromagnetic and/or superparamagnetic clusters far above the ambient temperature. 37,40 Actually both super-paramagnetic cluster model and super-antiferromagnetic cluster model are used to explain the possible presence of weak magnetism in the lead based multiferroics. R. Blinc et al has carried out the electron paramagnetic resonance (EPR) experiment on PFN ceramic and explains the presence of weak magnetization above Neel temperature in context of super paramagnetic cluster model.…”

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

“…A closely similar pattern is seen with increasing PZ content along the PZ-PFN join in Lidoped samples [42]. There is, however, great variability between samples, and weak ferromagnetism has been reported both at room temperature and at temperatures up to *530-580 K [28,[86][87][88][89] [47]. It remains possible that the weak room temperature ferromagnetism in PFN and PZT-PFN is due to the presence of some minor impurity phase, but Kuzian et al [90,91] have shown that ferrimagnetic ordering might occur in PFN, while Glinchuk et al [4] have shown how a nanodomain structure of local chemical ordering could lead to ferromagnetism in PZT-PFN.…”