Abstract
The structural, morphology, optical, electrical, and magnetic properties of Zn0.7MnxNi0.3−xO (x = 0.05, 0.1, 0.15, 0.2) nanoparticles synthesized by sol–gel technique have been systematically investigated by using X-ray diffractometer (XRD), scanning electron microscope (SEM), UV–vis-NIR spectrophotometer, impedance analyzer, and vibration sample magnetometer (VSM). XRD patterns reveal that all samples have hexagonal wurtzite structure along with secondary phases such as NiO and ZnMnO3. The average crystalline size increases with the increase in the Mn concentration in the host matrix. Diffuse reflectance studies (DRS) show an increment in optical band gap with increasing Mn content. AC conductivity of present samples has been studied as a function of frequency (100 Hz–10 MHz) of the applied AC signal in the temperature range of 323–463 K. The results showed that AC conductivity increases with an increase in frequency and temperature. The frequency exponent shows that small polaron conduction mechanism is the most favorable for all samples. The value of AC conductivity is observed to decrease with an increase in the Mn dopant concentration in the Zn0.7MnxNi0.3−xO system. At room temperature, magnetic characterization of the samples indicates the presence of both paramagnetic and ferromagnetic behavior. Magnetic saturation decreases with the increase in the Mn concentration in the host lattice.
Highlights
Semiconducting nanomaterials have attracted great scientific attention due to their unique properties for different nanotechnological potential applications (Jagadish & Pearton, 2006)
The diffraction pattern shows the segregation of secondary phases namely cubic NiO (JCPDS No 04-0835) and face-centered ZnMnO3 structure (JCPDS No 191461) besides the major hexagonal wurtzite structure corresponding to ZnO (Toloman et al, 2013; Tong et al, 2010)
The X-ray diffractometer (XRD) patterns indicate that the samples have secondary phases NiO and ZnMnO3 besides the major hexagonal wurtzite structure corresponding to ZnO
Summary
Semiconducting nanomaterials have attracted great scientific attention due to their unique properties for different nanotechnological potential applications (Jagadish & Pearton, 2006). The addition of TM dopant in ZnO induces dramatic changes in structural, thermal, optical, electrical, and magnetic properties. For Mn-doped ZnO nanoparticles many researchers have reported different magnetic behavior such as ferromagnetism (Jung et al, 2002), spin glass behavior (Fukumura et al, 2001), and paramagnetism (Tiwari et al, 2002). Nirmala, Smitha, and Anukaliani (2011) have studied the optical and electrical properties of (Mn, Co) co-doped ZnO nanoparticles synthesized by DC thermal plasma method. The substitution of Mn2+ ions in Ni-modified ZnO nanoparticles leads to the modification of structural, optical, electrical, and magnetic properties. The influence of different Mn concentrations on structural, optical, electrical, and magnetic studies has been investigated in the present work
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