The present invention relates to a ferrite particle, containing a crystal phase component containing a perovskite crystal represented by the compositional formula:

RZrO.sub.3 (provided that R represents an alkaline earth metal element), and having an apparent density in a range represented by the following formula:

1.90≤Y≤2.45

provided that Y in the formula is the apparent density (g/cm.sup.3) of the ferrite particle.

A ferrite sintered magnet has a ferrite phase having a magnetoplumbite-type crystal structure, and contains at least a metal element A, a metal element R, Fe, Co, Zn, and B. The element A is at least one kind of element selected from the group consisting of Sr, Ba, Ca, and Pb, and essentially includes Ca. The element R is at least one kind of element selected from the group consisting of Bi and rare-earth elements including Y, and essentially includes La. Atomic ratios of the metal elements satisfy the following expressions.

A.sub.1-rR.sub.rFe.sub.xCo.sub.yZn.sub.z  (1)

0.40≤r≤0.70  (2)

8.20≤x≤9.34  (3)

0.05<y≤0.50  (4)

0<z≤0.20  (5)

The content of Si is 0 to 0.60% by mass in terms of SiO.sub.2, and the content of B is 0.01 to 0.70% by mass in terms of B.sub.2O.sub.3.

The present disclosure is directed to methods of Quantum Spin Engineering of spinel superparamagnetic ferrite nanoparticles (SMFNs) for MRI contrast agents and for magnetohyperthermia agents. Using the methods herein, the magnetic properties of the SMFNs can be controlled by changing the amount of 3d-transition element cations having unpaired electrons in the 3d orbital that occupy the octahedral sites of the spinel crystal form, to form mixed spinels, while anions in the spinels can be utilized to magnetically couple the cations utilizing intra-crystalline angles determined by ion sizes and crystal structure, and further tuning of other critical parameters is provided. The mixed spinels disclosed herein provide enhanced MRI contrast agents and improved magnetohyperthermia agents with lower toxicity and safety concerns, while the production methods disclosed herein have lower cost.

The MnZn ferrite material includes principal components and auxiliary components, where the principal components include: 52.5 mol % to 53.8 mol % of Fe.sub.2O.sub.3, 8.8 mol % to 12 mol % of ZnO, and the balance of MnO; the auxiliary components include: 0.35 wt % to 0.5 wt % of Co.sub.2O.sub.3, 0.03 wt % to 0.08 wt % of CaSiO.sub.3, 0.01 wt % to 0.04 wt % of Nb.sub.2O.sub.5, and 0.05 wt % to 0.12 wt % of TiO.sub.2 and RE elemental components; the RE elemental components include one or more from the group consisting of 0 wt % to 0.04 wt % of Gd.sub.2O.sub.3, 0 wt % to 0.02 wt % of HO.sub.2O.sub.3, and 0 wt % to 0.03 wt % of Ce.sub.2O.sub.3; the auxiliary components are all represented by a mass percentage relative to a total mass of the Fe.sub.2O.sub.3, the MnO, and the ZnO.

A sintered MnZn ferrite comprising as main components 53.5 to 54.3% by mol of Fe calculated as Fe.sub.2O.sub.3, and 4.2 to 7.2% by mol of Zn calculated as ZnO, the balance being Mn calculated as MnO, and comprising as sub-components 0.003 to 0.018 parts by mass of Si calculated as SiO.sub.2, 0.03 to 0.21 parts by mass of Ca calculated as CaCO.sub.3, 0.40 to 0.50 parts by mass of Co calculated as Co.sub.3O.sub.4, 0 to 0.09 parts by mass of Zr calculated as ZrO.sub.2, and 0 to 0.015 parts by mass of Nb calculated as Nb.sub.2O.sub.5, per 100 parts by mass in total of the main components (calculated as the oxides), C.sub.(zn)/C.sub.(co) being 9.3 to 16.0 wherein C.sub.(zn) is the content of Zn contained as a main component (% by mol calculated as ZnO in the main components), and C.sub.(co) is the content of Co contained as a sub-component (parts by mass calculated as Co.sub.3O.sub.4 per 100 parts by mass in total of the main components).

A MnZn-based ferrite that can reduce the loss even when a high-frequency voltage fluctuation occurs is provided. The above MnZn-based ferrite is a MnZn-based ferrite including Fe2O3, ZnO, and MnO as main components, in which Fe2O3 is 53.2 to 56.3 mol % and ZnO is 1.0 to 9.0 mol %, with a balance of MnO, in 100 mol % of the main components, and the MnZn-based ferrite includes 0.9 to 2.0% by mass of Co.sub.2O.sub.3, 0.005 to 0.06% by mass of SiO.sub.2, and 0.01 to 0.06% by mass of CaO, as auxiliary components, per 100% by mass of the main components.

In additive manufacturing operations, powders used in stereolithographic processes need to be precisely spread out in a uniform fashion at every pass of the stereolithographic process to ensure predictability in powder surface morphology. Typically, this is difficult to achieve with conventional powders because often these powders suffer from poor flowability, which may further deteriorate over time, and impairs the efficiency of the stereolithographic processes. The present disclosure describes additive manufacturing powders having improved physical characteristics such as flowability and tap density, which are less sensitive or insensitive to ambient humidity. For example, there is described a powder that includes spherical particles having a particle size distribution of less than 1000 micrometers and having a measurable flowability as determined in accordance with ASTM B213 at 75% relative humidity.

The present invention provides: a ferrite particle containing a crystal phase component containing a perovskite crystal represented by the compositional formula RZrO.sub.3 (where R is an alkaline earth metal element); and an electrophotographic developer carrier core material, an electrophotographic developer carrier, and an electrophotographic developer containing the ferrite particles.

The invention provides a ceramic composite oxide of formula (I): (1−x)AaBbOy+xCcDdOz (I) wherein A, B, C and D are each independently selected from the group consisting of Li, Na, Mg, Al, P, K, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sr, Y, Zr, Nb, Mo, Ru, In, Sn, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Er, Tm, Yb, Lu, Ta, W, Bi and mixtures thereof; x is 0.05 to 0.95; y and z are balanced by the charge of the cations; 0≤a, b, c, d≤1; and wherein said ceramic composite oxide has an average particle size diameter of 10 to 700 nm.

Superparamagnetic nanocomposites are provided. In an embodiment, a superparamagnetic nanocomposite comprises a superparamagnetic core comprising a first, soft superparamagnetic ferrite and a superparamagnetic shell comprising a second, soft superparamagnetic ferrite, the shell formed over the core, wherein the first and second soft superparamagnetic ferrites are different compounds and have different magnetocrystalline anisotropies.