Solubility limit, magnetic interaction and conduction mechanism in rare earth doped spinel ferrite

Abstract

In present review we have focused various issues like solubility limit, magnetic interaction and conduction mechanism of rare earth doped ferrite. Cumulative effects of valence state, magnetic moments of rare earth ions, weakening/strengthening of exchange interaction and magnetic ordering in rare earth ion doped ferrite are responsible for magnetic behavior. It is proposed that characterization techniques based on synchrotron radiation like X-ray absorption spectroscopy and X-ray magnetic circular dichroism can open pathways to prove these assumptions.Keywords: Rare earth, ferrites, magnetic interaction, valence state 1.INTRODUCTIONSpinel ferrites are ferrimagnetic material which have numerous technological applications [1][2][3]. Moreover, nanoparticles of these ferrites are being utilized in high-density magnetic information storage, magnetic resonance imaging, drug delivery etc. [4][5][6]. These several applications are based on magnetic and electrical behavior of ferrites [1][2][3][4][5][6]. These properties depend on various factors like, ionic radii, nature of hybridization, presence of doped atom in host lattice apart from the particle size [7][8][9][10]. Thus, research is being carried out for doped ferrite systems in order to understand the altered behavior and to optimize them for different applications [11][12][13][14][15]. In recent years, rare earth (RE) doped ferrites become interesting due to their superiority for various applications over other doped ferrite systems [17][18][19][20][21][22]. These systems become radioactive and exhibit potentential for biomedical applications [19] along-with efficient tumor passive targeting [23]. Improved capability of dye removal [24], waste water treatment [25], degradation of organic pollutants through photocatalytic activity [26] are other important fields of utilization of these ferrites. These ferrites exhibit enhanced magneto optical kerr (MOKE) effect [20] and excellent microwave absorption properties [21,22]. Thus, these ferrites cover a wide range of applications chiefly based on their magnetic characteristics [17][18][19][20][21][22][23][24][25]. However, there is lack of understanding of magnetic interaction, conduction mechanism inside these ferrites [15,16]. Thus purpose of this review article is to discuss these issues and to give prospects for future research in this direction. SPINEL FERRITEThe general formula for spinel ferrite is MO:Fe2O3 where, M is a divalent transition metal ion. Spinel name is given due to resemblance of structure of these ferrites with mineral spinel MgO.Al2O3. In this structure, oxygen ions are packed quite close together in face centred cubic arrangement and metal ions occupy spaces between them (Fig. 1). These spaces are categorized as tetrahedral (A) and octahedral (B) sites when surrounded by four and six oxygen ions respectively (Fig. 1).In a unit cell of spinel ferrite, there exists 64 and 32 A and B-sites respectively. Only 1/8 th and 1/2 th of A and B-sites are occupied [27]. Metal ions are distributed among A a...

A Theoretical Approach: Effects of <i>Mn</i> Substitution in <i>Cobalt</i> Ferrite

“…But I JKLLM is found to increase for Co 1+x Mn x Fe 2-x O 4 as shown in Figure 6 because of concurrent addition of Co along with Mn substitution for Fe, which may lead to supersede the effect of longer hopping lengths through the formation of new probable phases due to more influence of inherent ferromagnetic ordering of Co in this system. This is found in agreement with the recently published experimental result [10,14]. Thus this eventual variation ofI JKLLM leads to predict that thermally fluctuated magnetic ions require more thermal energy ( κ] ) inCo 1-x Mn x Fe 2 O 4 (where Mn substituted for Co) than inCoMn x Fe 2-x O 4 (where Mn substituted for Fe) to decrease spontaneous magnetization, which is indicative to make T C tunable by adjusting Mn content and almost in agreement with published experimental result [13].…”

“…Hence, the exchange interaction between A and B sites lead CoFe 2 O 4 ferrite to possess ferrimagnetic behavior due to magnetic moments of bivalent cations M 2+ (Co 2+ ) in the B position as reported in the literature [9]. Accordingly, the effective magnetic moment I JKLLM for inverse spinel structure may be estimated by the following equation, modified from the formula of normal spinel structure [10] as:…”

“…Superparamagnetic behavior is the exclusive property of magnetic nanoparticles and found to arise when the thermal energy fluctuations or an applied field can easily move magnetic moments away from the easy axis (The preferred crystallographic axes for the magnetic moment are to point along). Then each particle behaves like paramagnetic atom but with giant magnetic moment owing to sustained magnetic order [10]. The giant magnetic moment may be thought of as the determining factor of superparamagnetism in CoFe 2 O 4 ferries, which may depend on the hopping lengths and in turn, on lattice constant 'a'.…”

Study on AC permeability and permittivity of manganese doped cobalt ferrite nanoparticles

“…Cobalt ferrites are reported to be the best example of hard ferrite materials because of their excellent chemical stability, mechanical hardness, reasonable saturation magnetization and high magneto-crystalline anisotropy [1]. They are now being used in high-density recording media, ferro-fluids, magnetic resonance imaging (MRI), biomedical diagnostics, radio frequency hyperthermia and drug delivery as reported elsewhere in literatures [1][2][3][4][5][6][7][8][9][10][11][12]. Cobalt ferrite is of inverse spinel structure with basic formula B (AB) O 4 where relatively larger oxygen ions (O 2 − ) form cubic closed pack (ccp) structure.…”

The influence of selected ions on various characteristics of Nickel-Zinc ferrites

“…Moreover, these large ions could probably cause lattice distortion which determines of the solubility of RE 3+ in the spinel structure; the overcome of solubility limit leads to the formation of the secondary phases. These secondary phases are usually the orthoferrite and oxides of RE [7].…”