Effect of nanometric grain size on room temperature magnetoimpedance, magnetoresistance, and magnetic properties of La0.7Sr0.3MnO3 nanoparticles

Abstract

In this paper we have investigated the effect of nanometric grain size modulation on the behavior of magnetoimpedance (MI), magnetoresistance, and magnetic properties of a series of single-phase nanocrystalline colossal magnetoresistance La0.7Sr0.3MnO3 (LSMO) manganites all synthesized through chemical route “pyrophoric reaction process.” MI measurements were carried out at room temperature (T=300K) in the ac signal frequency (f) range of 40kHz-110MHz and in dc magnetic field (H) range of −2.5kOe<H<+2.5kOe, respectively. The experimental results show that MI% increases with the increase in nanometric grain size (ϕ) for this series of samples. This behavior can be explained in the light of classical electrodynamics, which relates this effect with the dependency of skin depth on external magnetic field and applied ac signal frequency. Interestingly, MI of about 92% was obtained for the 28nm LSMO sample at a frequency (f) of 10MHz and at H=2.5kOe. The same sample also showed a maximum MI sensitivity of about 1%/Oe near 60Oe dc magnetic field at f=10MHz. Magnetization measurements were carried out in the applied magnetic field range of −5kOe<H<+5kOe and the experimental results reveal that spontaneous magnetization decreases with decrease in particle size. These nanometric LSMO samples also showed a paramagnetic-ferromagnetic transition near TC=360K. For comparison, we have also presented room temperature low-field magnetoresistance (LFMR) study of this series of LSMO nanoparticles. This study reveals that within this particle size range, 14–28nm, LFMR decreases with decrease in particle size, which in fact mimics the variation of MI with particle size.

Synthesis of magnetoresistive La0.7Sr0.3MnO3 nanoparticles by an improved chemical coprecipitation method

“…5. It is clear that the sample shows a good ferromagnetic behaviour at room temperature and the value of saturation magnetization (M s ) comes out to be 30 emu/g, which is similar to the previous results by the pyrophoric reaction process [20].…”

Magnetic Properties of Interacting La0.67Sr0.33MnO3 Nanoparticles

“…By increasing the particle size, the spontaneous magnetization and curvature are increased which indicates that the magnetic order in the samples are increased. This behavior has been also reported for LSMO nanoparticles [26,27].…”

“…From Fig. 4, Arrott plot shows a strong convex curvature with a finite spontaneous magnetization which is a signature of ferromagnetic phase of the samples [26,27]. Spontaneous magnetization can be estimated by linear fitting of the high magnetic field part of the M 2 -H/M curve and intercepts it with the M 2 axis.…”

Sample thickness dependence of giant magnetoimpedance under low fields for La0.67Sr0.33Mn0.98Co0.02O3 manganites

“…The spin-polarized tunneling through the interfaces of grains or spin-dependent scattering at grain boundaries has been suggested to be responsible for the LFMR [5,6]. In addition to CMR and LFMR, La 1-x A x MnO 3 based manganites also exhibit colossal magnetoabsorption in the microwave highfrequencies (∼GHz) [7,8] and giant magnetoimpedance in radio frequencies (∼MHz) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. For metallic manganites below Curie temperature, a high frequency current passes the sample mainly through its surface region characterized by the penetration depth ı = 2 / 0 t ω ( is the resistivity, 0 vacuum permeability, t transverse permeability of material, ω the angular frequency of current) and a strong magnetoimpedance could occur, which originates from the variation of t induced by the applied DC magnetic field, via the change of penetration depth ı.…”