Low vanadium narrow linewidth magnetic material for firing with dielectric materials without an interfacial reaction region

Abstract

A magnetic assembly for use in a circulator application that includes a ferrite- based material having an elemental formula that identifies a number of formula units for each element in the formula; the elemental formula including both the elements of vanadium and aluminum with the number of formula units (x) for vanadium being less than or equal to 0.22 and the number of formula units (y) for aluminum being less than 0.60; and a dielectric material that surrounds at least a portion of the ferrite-based material. The ferrite-based material and the dielectric material directly form a chemical bond there between in the absence of any polymers, adhesives or glues. The ferrite- based material may include the composition described by the formula Y2.28Cao.72Fe4.23Zro.32VxAlyO12, wherein 0.15 < x < 0.22, 0.0 < y < 0.6, and 0.15 < x+y < 0.75.

Description

LOW VANADIUM NARROW LINEWIDTH MAGNETIC MATERIAL FOR FIRING WITH DIELECTRIC MATERIALS WITHOUT AN INTERFACIAL REACTION REGIONField

[0001] The present disclosure generally relates to magnetic assemblies used in circulator applications. More specifically, the present disclosure describes a ferrite- based material that can be fired with a dielectric material to form a magnetic assembly.Background

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] Circulators represent passive magnetic devices or assemblies that are generally used in high frequency (e.g. microwave, radio) systems, such as communication systems, radar systems, and mobile phone networks. These three- port passive devices allow a signal to pass in one circular direction (e.g., clockwise from one port to another port in the device) while providing high isolation to reflected energy in the reverse direction (in the counterclockwise direction). These devices primarily function by utilizing a magnetic field applied to an insulating ferrite disk to control the direction of radio / microwave frequency signals within the device.

[0004] Commercially available circulators generally comprise a disk or rod made of a magnetic oxide material surrounded by a ring of a dielectric material. This dielectric material ring is commonly adhered to a surface of the magnetic oxide material through the use of a polymer-based adhesive or glue. However, the use of an adhesive or glue does not represent an ideal situation because polymer-based materials tend to increase the insertion loss exhibited by the device. In other words, the incorporation of such adhesive(s) or glue(s) increase the amount of energy lost when a radio / microwave signal is transmitted from one port of the device to another port.

[0005] Attempts to surmount this problem have resulted in the formation of magnetic devices in which the magnetic oxide material component has been first fired to greater than 98 % theoretical density followed by the subsequent firing of the dielectric material ring directly onto the already sintered magnetic oxide material in order to form an inorganic bond in the absence of any polymer-based adhesive or glue. However,Attorney Docket No. 106191-171 many metallic elements such as vanadium, used as an additive to reduce the saturation magnetization of the ferrite with a minimal impact on the Curie temperature may diffuse into the dielectric ring and cause solid state reactions which may increase the susceptibility of the magnetic assembly to dielectric breakdown under high applied electric potentials. Thus, the creation of compositions for magnetic oxide materials that are capable of being directly bonded to dielectric materials with minimal impact on the Curie temperature of the magnetic oxide material while also reducing the susceptibility of the resulting magnetic assembly to dielectric breakdown is desirable.Drawings

[0006] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings.

[0007] Fig.’s 1A & 1 B represent schematic top-down and perspective views of ferritebased oxide materials and dielectric materials, as well as a magnetic assembly formed therefrom according to the teachings of the present disclosure.

[0008] Fig. 2 is a top-down view of a magnetic assembly (A, B) demonstrating that the thermal reaction between a conventional vanadium doped ferrite material and dielectric ring results in a discoloration of the materials that enhances susceptibility of the magnetic assembly to dielectric breakdown.

[0009] Fig. 3 is a table that summarizes the magnetic and electric properties measured for a vanadium-aluminum hybrid doped ferrite-based material formed according to the teachings of the present disclosure.

[0010] Fig. 4 is a graphical representation of normalized change in magnetization plotted as a function of temperature used to determine the Curie temperature of a vanadium-aluminum hybrid doped ferrite-based material formed according to the teachings of the present disclosure.

[0011] Fig. 5 is a top-down view of a magnetic assembly (C, D) demonstrating that the thermal reaction between a vanadium-aluminum doped ferrite-based material and a dielectric material according to the teachings of the present disclosure results in minimal discoloration of the materials thereby indicating little to no enhancement in the susceptibility of the magnetic assembly to dielectric breakdown.Attorney Docket No. 106191-171

[0012] Fig. 6 is a table that compares the leakage current exhibited by magnetic assemblies A & B of Fig. 2 to the leakage current exhibited by magnetic assemblies C & D of Fig. 5.

[0013] Fig. 7 is a flowchart demonstrating a process of forming the magnetic assemblies according to Fig.’s 1 A & 1 B.

[0014] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. It should be understood that throughout the description and drawings, corresponding reference numerals indicate like or corresponding parts and features.Detailed Description

[0015] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. For example, the vanadium-aluminum hybrid doped ferrite-based material prepared and used according to the teachings contained herein are described throughout the present for use in a disk-shaped circulator in order to more fully illustrate the structural elements and the use thereof. The incorporation and use of such ferrite-based materials in other applications, including without limitation as an isolator, duplexer, or reflection amplifier, or in a different geometric shape that has rotational symmetry is contemplated to be within the scope of the present disclosure.

[0016] For the purpose of this disclosure, terms “circulator” and “isolator” may be used interchangeably or separately, depending on applications as generally understood. For example, circulators are three-port passive devices utilized in RF applications to selectively route RF signals between an antenna, a transmitter, and a receiver. If one of the three ports in a circulator is connected to ground, the device allows the RF signal to proceed in one direction while being blocked in the opposite direction, such a circulator is referred to as an isolator.

[0017] Referring to Fig.’s 1A & 1 B, the present disclosure generally provides a magnetic assembly 1 for use in a circulator application. This magnetic assembly 1 comprises a ferrite-based material 5a, 5b and a dielectric material 10a, 10b that surrounds at least a portion of the ferrite-based material 5a, 5b. In this magnetic assembly 1 , the ferrite-based material 5a, 5b and the dielectric material 10a, 10b directly form a chemical bond there between. The chemical bond formed directly between the ferrite-based material 5a, 5b and the dielectric material 10a, 10b in theAttorney Docket No. 106191-171 magnetic assembly 1 is substantially free of any organic polymers, adhesives, or glues. This chemical bond is formed by a thermally induced reaction that occurs between the ferrite-based material 5a, 5b and the dielectric material 10a, 10b.

[0018] The shape of the ferrite-based material 5a, 5b may be a disk (Fig. 1A), a rod (Fig. 1 B) or any other geometric shape that can be configured to provide rotational symmetry, such as without limitation, a triangle. The diameter and height of the ferrite- based material is dependent upon the signal frequency for which it is utilized. Basically, the diameter and height of the ferrite-based material is predetermined in order to allow the desired or dominant signal mode to propagate, while suppressing higher order modes. Alternatively, the ferrite-based material includes a periphery that is circular in shape.

[0019] When the ferrite-based material 5a is a circular disk (Fig. 1 A) having diameter Ddisk, the dielectric material 10a is a ring defined by an inner diameter Djnand an outer diameter Dout. In this case, the inner diameter Din is smaller than the diameter Ddisk of the circular disk and the outer diameter Dout is equal to the diameter Ddisk of the circular disk. The height Hdisk of the ferrite-based disk and the height Hringof the dielectric material are determined as previously stated based on the ability to propagate the desired signal.

[0020] When the ferrite-based material 5b is a rod (Fig. 1 B) having a diameter DrOd, the dielectric material 10b remains a ring defined by an inner diameter Din and an outer diameter Dout. However, in this case, the inner diameter Djnis equal to or the same as the diameter DrOd of the rod and the outer diameter Dout is greater than the diameter Drod of the ferrite-based rod. The height HrOd of the ferrite-based rod and the height Hring of the dielectric material are generally similar, such that the dielectric material surrounds the surface of the rod.

[0021] The composition of the dielectric material 10a, 10b used as the ring in the magnetic assembly 1 may comprise any metal oxide material known for use as a dielectric material in a similar application. Several dielectric oxide materials utilized in this capacity include, without limitation, oxides of barium, zirconium, zinc, tantalum, magnesium, calcium, and titanium, as well as mixtures and combinations thereof. Although many different dielectric materials may be utilized, the most common commercially available dielectric materials 10a, 10b are based on a magnesium calcium titanate system. One example of a material in this type of system comprises (1-x)MgTiO3 - xCaTiOs, wherein 0.00 < x < 0.3. Alternatively, the dielectric materialAttorney Docket No. 106191-17110a, 10b used as the ring in the magnetic assembly 1 comprises a material based on a magnesium calcium titanate system or other compositions as taught in US patent no. 7,687,014, the entire contents of which are hereby incorporated by reference.

[0022] Ferrite-based materials, including spinel, hexagonal, or garnet ferrites exhibit suitable microwave characteristics. Many microwave magnetic materials comprise derivatives of yttrium iron garnet (YIG). YIG is a synthetic form of a garnet that has found broad use largely because of its narrow linewidth at the ferromagnetic resonance frequency. Garnets represent crystalline materials that exhibit ferromagnetic properties that are particularly useful in RF electronics, which operate in the lower frequency portions of the microwave region (< 10 GHz). In addition, various synthetic garnets (or generally ferrites / ferrite garnets) enable size reduction of RF components such as isolators and circulators, in part due to their high dielectric constants. Alternatively, the ferrite-based material is based on a yttrium iron garnet as further defined herein.

[0023] Yttrium iron garnets (YIG) are generally composed of yttrium, iron, and oxygen, having a composition of Y3Fe2(FeO4)3 or YsFesOu. However, these ferrite- based materials may include one or more other metals as “dopant” elements to adjust the magnetic properties of the ferrite. Some dopant elements may decrease the overall saturation magnification exhibited by the ferrite-based material. In addition, these dopant elements may also decrease the Curie temperature exhibited by the ferrite-based materials, and increase the susceptibility of the magnetic assembly to dielectric breakdown, or both.

[0024] In a circulator application, it is generally desirable to maintain the Curie temperature as high as possible since the Curie temperature for a ferrite-based material represents the temperature at which the material loses its magnetic properties upon transitioning from a ferrimagnetic state to a paramagnetic state. In other words, the Curie temperature represents the temperature at which thermal energy overcomes the existing magnetic forces that align the magnetic dipoles within the ferrite structure. Essentially, the Cure temperature is the critical point at which the ferrite ceases to exhibit magnetism when heated to a higher temperature.

[0025] A variety of dopant elements may be incorporated into the ferrite-based material. Several examples of such dopant elements include, without limitation, gadolinium, samarium, tin, titanium, indium, cobalt, manganese, gallium, vanadium, aluminum, calcium, zirconium, zinc, and combinations thereof. Vanadium representsAttorney Docket No. 106191-171 one element that upon incorporation into a ferrite-based material decreases the saturation magnetization, while exhibiting a reduced impact on the Curie temperature exhibited by the material (i.e., relative to other dopants elements). A suite of ferritebased materials utilizing vanadium as a dopant exists with a saturation magnetization ranging from about 800 gauss to about 1 ,900 gauss with the lower saturation magnetization materials containing larger amounts of vanadium.

[0026] However, the use of vanadium as a dopant element presents a practical problem for lower saturation magnetization garnet ferrites in that the vanadium reacts with the material in the dielectric ring causing a thick region of discoloration in the ring and ferrite material. The presence of this discoloration in the materials that form the magnetic assembly is indicative of a solid state chemical reaction which causes the magnetic assembly to be susceptible to dielectric breakdown under high applied electric potentials.

[0027] Referring now to Fig. 2, a conventional magnetic assembly 2 is shown in which a comparable ferrite material 5c formed in the shape of a disk is directly coupled to a dielectric ring 10a, 10b in the absence of any adhesive or glue. The comparable ferrite material 5c used in Fig. 2 corresponds to a composition comprising yttrium iron garnet doped with calcium, zirconium, and vanadium. More specifically, the elemental composition and formula units for each element in the comparable ferrite material shown in Fig. 2 is provided by Formula F-1 :Y 1 7sCai 22Fe4.23Zr.32V.45O12. F-1This comparable ferrite material exhibits a Curie temperature of 217°C and a saturation magnetization between 1 ,250 gauss and 1 ,270 gauss.

[0028] The difference between the magnetic assemblies 2 further identified as “A” or “B” in Fig. 2 is the use of a different lot (e.g., batch) of the same dielectric material to form the ring 10a, 10b. In both magnetic assemblies (A & B) shown in Fig. 2, a reaction between the comparable ferrite material 5c and the dielectric material 10a, 10b leads to the formation of a large discoloration region 15 in the dielectric ring and / or ferrite material 5c. This discoloration region 15 has been observed to correlate with an increase in the susceptibility of the magnetic assemblies 2 to dielectric breakdown. The formation of this large discoloration region 15 results from the reaction of the comparable ferrite material 5c and the dielectric material 10a, 10b has been observedAttorney Docket No. 106191-171 not only in magnetic assemblies that exhibit a saturation magnetization of about 1 ,200 gauss, but also in magnetic assemblies that exhibit a saturation magnetization greater than 1 ,600 gauss.

[0029] Surprisingly, the practical problem identified above in which the susceptibility of the magnetic assembly to dielectric breakdown increases upon using vanadium as a dopant element in the ferrite-based material can be eliminated or reduced upon using both vanadium and aluminum as hybrid dopant elements in the ferrite-based material. More specifically, this practical problem is resolved upon forming a ferrite- based material where aluminum and vanadium are used together as hybrid dopant elements provided the level of vanadium is capped at 0.22 formula (x) units and the level of aluminum is less than 0.60 formula (y) units. Alternatively, the ferrite-based material contains 0.15 < x < 0.22, where x is the number of formula units of vanadium and 0.0 < y < 0.6, where y is the number of formula units of aluminum. Alternatively, the sum of the formula units for vanadium and aluminum (i.e., x + y) is in the range of 0.15 < x + y < 0.75.

[0030] According to one aspect of the present disclosure, the ferrite-based material may comprise one or more yttrium iron garnets doped with various amounts of calcium, zirconium, vanadium, and aluminum. The elemental composition of this yttrium iron garnet may be described, without limitation, as shown by formula F-2,Y 3-z-2xCaz+2x F ©5-x-y-zAzV xAl y012 , F-2 with A being Ti, Zr, or Sn, wherein the formula unit (z) is given by 0 < z < 0.6 and the formula units (x) for vanadium and (y) for aluminum are provided as previously described above. The saturation magnetization (4TTMS) for the ferrite-based material of the present disclosure may range from at least 600 gauss to about 2,000 gauss; alternatively, from about 800 gauss to about 2,000 gauss; alternatively, from about 1 ,100 gauss to about 1 ,800 gauss; alternatively, from about 1 ,200 gauss to about 1 ,600 gauss; alternatively, the saturation magnetization is at least 1 ,200 gauss.

[0031] One specific composition of a ferrite-based material was formed having the composition shown in formula F-3 below. The magnetic and electrical properties measured for this ferrite-based material (formula F-3) are summarized in the table provided as Fig. 3. The electrical & magnetic properties for this ferrite-based material was measured three times (tests i-iii) in order to determine any variability associatedAttorney Docket No. 106191-171 with the test measurements. For example, the saturation magnetization (4TTMS) measured for this ferrite-based material varied from 1 ,255 to 1 ,266 gauss. This ferrite- based material composition was selected because it provided both similar electrical and magnetic properties as the comparable ferrite material previously discussed above corresponding to formula F-1. The difference between the ferrite-based material formed according to the present disclosure as described in formula F-3 and the comparable ferrite material previously described in formula F-1 is the presence of a hybrid vanadium-aluminum dopant in the material of the present disclosure (formula F-3) as compared to the presence of only a vanadium as the dopant (e.g., no aluminum) in the comparable material (formula F-1).Y2.2sCao 72Fe4.23Zr0.32V0.20AI0.25O12 F-3

[0032] Referring now to Fig. 4, the normalized change in saturation magnetization (A4 MS) for the ferrite-based material of formula F-3 is plotted as a function of temperature. Extrapolation of the resulting curve is used to identify the point (*) on the curve where the magnetization approaches zero. This point represents the Curie temperature (Tc) for the magnetic material, which corresponds to the maximum temperature above which the material loses its magnetic interaction. As the operating temperature of a magnetic assembly, such as a circulator, approaches the Curie temperature, the saturation magnetization is reduced. Typically, a higher Curie temperature provides for the use of a higher operational temperature for the magnetic assembly without a need for external compensation.

[0033] As shown in Fig. 4, the Curie temperature exhibited by the ferrite-based material described in formula F-3 is 207°C. In comparison, the comparable ferrite- based material described by the composition shown in formula F-1 has a Curie temperature of 217°C. Thus, the presence of aluminum as part of the vanadiumaluminum dopant in the comparable ferrite material (formula F-3) maintains the Curie temperature within about 95.4% of the Curie temperature exhibited by the comparable ferrite material (formula F-1 ) comprising vanadium as the dopant element. Although the presence of aluminum used as part of the hybrid vanadium-aluminum dopant slightly decreases the Curie temperature of the ferrite-based material (formula F-3), the modest decrease, e.g., about 10°C, can easily be compensated for by the addition of a metallic magnetic material in the circulator device.Attorney Docket No. 106191-171

[0034] The Curie temperature of the ferrite-based material containing the hybrid vanadium-aluminum dopant elements of the present disclosure may be > 155°C; alternatively, > 185°C; alternatively, > 200°C; alternatively, > 205°C; alternatively, > 207°C. Alternatively, the ferrite-based material in the magnetic assembly of the present disclosure has a Curie temperature (Tc) that is less than 20%, alternatively, less than 10%, alternatively, less than 7.5%, alternatively, less than about 5.0% lower than the Curie temperature of a similar ferrite material in a similar magnetic assembly that comprises vanadium as an element and in which the formula units for an aluminum element is 0.00; the similar ferrite material having the same saturation magnetization as the ferrite-based material..

[0035] Referring now to Fig. 5, a magnetic assembly 1 is shown in which a ferrite- based material 5a according to the present disclosure is formed in the shape of a disk and directly coupled to a dielectric ring 10a, 10b in the absence of any polymer, adhesive or glue. The ferrite-based material 5a used in Fig. 5 corresponds to the composition described by formula F-1. The difference between the magnetic assemblies 1 further identified by “C” or “D” in Fig. 5 is the use of a different lot (e.g., batch) of the same dielectric material to form the ring 10a, 10b. The dielectric material used in the magnetic assembly 1 labeled as “C” in Fig. 5 represents the same batch of dielectric material used to form the conventional magnetic assembly 2 identified as “A” in Fig. 2. Similarly, the dielectric material used in the magnetic assembly 1 labeled as “D” in Fig. 5 is the same batch of dielectric material used to form the conventional magnetic assembly 2 identified as “B” in Fig. 2.

[0036] In both magnetic assemblies (C & D) shown in Fig. 5, a reaction between the ferrite-based material 5a and the dielectric material 10a, 10b results in a bond that minimizes the formation of any discoloration region 20. A comparison of the discoloration region 20 in the magnetic assemblies (C & D) shown in Fig. 5 with the discoloration region 15 observed to occur for the comparable magnetic assembly (A & B) shown in Fig. 2 demonstrates that the bonding of the dielectric material rings 10a, 10b to the ferrite-based disk 5a formed with the hybrid vanadium-aluminum dopant elements of the present disclosure reduces and / or minimizes any increase in the susceptibility of the magnetic assembly 1 to dielectric breakdown. In other words, the reduced formation of a discoloration region 20 (Fig. 5) or lack thereof in a magnetic assembly 1 that incorporates the ferrite-based material of the present disclosure comprising the hybrid vanadium-aluminum dopant elements as compared to theAttorney Docket No. 106191-171 discoloration region 15 (Fig. 2) in a magnetic assembly 2 that incorporates a comparable ferrite material containing a vanadium dopant with both magnetic assemblies 1 , 2 exhibiting the same saturation magnetization demonstrates a reduction or minimization in the susceptibility of the magnetic assembly 1 to dielectric breakdown resulting from the formation of a direct chemical bond between the ferrite- based material and the dielectric material.

[0037] In additon, the measurement of leakage current that occurs at high potentials for magnetic assemblies (C & D) further demonstrates beneficial properties associated with the ferrite-based material of the present disclosure. The ferrite-basd material of the present dsiclosure, which containis the hybrid vanadium-aluminum dopant elements, reduces the magnitude of the leakage current as compared to the leakage current measured for the comparable magnetic assemblies (A & B). Referring now to Fig. 6, the leakage currents measured for magnetic assemblies A & B (Fig. 2) and C & D (Fig. 5) are summarized. For each magnetic assembly A, B, C, D, measurements were taken on a total of 20 identical assemblies in order to determine the average leakage current and the statistical significance thereof.

[0038] As shown in Fig. 6, the leakage current measured for magnetic assemblies C & D are substantially smaller than the leakage current measured for magnetic assemblies A & B. The t-tests conducted in regard to each magnetic assembly demonstrate that this difference is statistically significant. These t-tests further demonstrate that different lots or batches of the dielectric material may also contriubute to a difference in the leakages currents exhibited by the magnetic assemblies. This result is observed upon comparison of the leakage current meassured for magnetic assembly A with the leakage current measured for magnetic assembly B or upon comparison of the leakage current measured for magnetic assembly C with the leakage current measured for magnetic assembly D.

[0039] However, comparison of the leakage current measured for magnetic assembly A with the leakage current measured for magnetic assembly C or upon comparison of the leakage current measured for magnetic assembly B with the leakage current measured for magnetic assembly D confirms that a statistically significant reduction in leakage current results from the use of a ferrite-based material formed with the hybrid vanadium-aluminum dopant of the present disclosure (see formula F-3) as compared to the comparable ferrite material formed with only a vanadium dopant (see formula F-1 ). The only difference between magnetic assemblyAttorney Docket No. 106191-171A and magnetic assembly C or between magnetic assembly B and magnetic assembly D is that magnetic assemblies A & B include the comparable or conventional ferrite material formed with only a vanadium dopant (see formula F-1 ), while magnetic asssemblies C & D include the ferrite-based material formed with the hybrid vanadiumaluminum dopant of the present disclosure (see formula F-3). In other words, magnetic assemblies A and C utlilze the same lot or batch of dielectric material. Similarly, magnetic assemblies B and D utilize the same lot or batch of dielectric material.

[0040] Upon substitution of the comparable ferrite material (formula F-1 ) in magnetic assembly A for the ferrite-based material (formula F-3) of the present disclosure in magnetic assembly C, the average leakage current decreases from 2.027 pA to 0.574 pA. This reduction corresponds to a leakage current in magnetic assembly C that is equivalent to about 28.3% of the leakage current observed in magnetic assembly A. A similar reduction in leakage current is observed upon comparison of magnetic assembly B with magnetic assembly D. In this case, upon substitution of the comparable ferrite material (formula F-1 ) in magnetic assembly B for the ferrite-based material (formula F-3) of the present disclosure in magnetic assembly D, the average leakage current decreases from 1 .570 pA to 0.482 pA, which corresponds to a leakage current in magnetic assembly D that is equivalent to about 30.7% of the leakage current observed in magnetic assembly B. Thus, the chemical bond between the ferrite-based material (formulas F-2, F-3) that incorporates the hybrid vanadiumaluminum dopant elements and the dielectric material of the present disclosure reduces the average leakage current of the magnetic assembly to less than 35% of the average leakage current exhibited by a similar magnetic assembly containing a similar ferrite material that includes a vanadium dopant with the formula units for aluminum element being 0.00 and in which the similar ferrite material exhibits the same saturation magnetization as the ferrite-based material of the present disclosure. Alternatively, the average leakage current of the magnetic assembly comprising the ferrite-based material of the present disclosure is less than 1 / 3 of the leakage current of a comparable magnetic assembly comprising the similar or comparable ferrite material; alternatively, the average leakage current is between about 25% and 35%; alternatively, about 30% of the leakage current exhibited by the comparable magnetic assembly.Attorney Docket No. 106191-171

[0041] According to another aspect of the present disclosure a method of fabricating a magnetic assembly is provided. Referring now to Figure 7, this process 25 generally comprises providing 30 a ferrite-based material in the form of a disk or rod; the ferrite- based material including hybrid vanadium-alumina dopant elements; providing 35 a dielectric material in the form of a ring; placing 40 a surface of the dielectric material in direct contact with a surface of the ferrite-based material; and co-firing 45 the ferrite- based material and the dielectric material, thereby attaching the dielectric material to the ferrite-based material via a chemical bond. The chemical bond that is formed directly between the ferrite-based material and the dielectric material in the magnetic assembly is substantially free of any organic polymers, adhesives, or glues.

[0042] The process 25 for providing the magnetic assemblies of the present disclosure may be accomplished by forming the ferrite-based materials using any known or available ceramic techniques. When desirable, the ferrite-based materials may be sintered while forming the disk or rod shape prior to being used to form the magnetic assembly.

[0043] The co-firing of the ferrite-based material and the dielectric material together to form a chemical bond there between may be done at a temperature that is > 750°C; alternatively, > 900°C; alternatively, > 1 ,000°C; alternatively, > 1 ,100°C or in fact any temperature below the sintering temperature of the ferrite material without exceeding the scope of the present disclosure. The chemical bond formed between the ferrite- based material and the dielectric material is the result of a thermally induced solid- state reaction. A chemical bond created by thermal reaction generally involves the use of thermal energy to initiate a chemical reaction between the materials where new bonds are formed between atoms in the materials. The application of heat essentially causes a reaction between two or more elements to form bond(s) there between.

[0044] From the foregoing description, it will be appreciated that although several materials, techniques, and aspects of forming a magnetic assembly have been described with a certain degree of particularity, it is obvious that many changes can be made in the specific designs, compositions, and methodology as described above without departing from the spirit and scope of this disclosure.

[0045] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention. For example, it will be appreciated that all preferredAttorney Docket No. 106191-171 features described herein are applicable to all aspects of the invention described herein.

[0046] Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include or do not include, certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required for one or more embodiments.

[0047] For the purpose of this disclosure, the terms "at least one" and "one or more of” an element are used interchangeably and may have the same meaning. These terms, which refer to the inclusion of a single element or a plurality of the elements, may also be represented by the suffix "(s)"at the end of the element. For example, "at least one metal", "one or more metals", and "metal(s)" may be used interchangeably and are intended to have the same meaning.

[0048] Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than or equal to 10% of, within less than or equal to 5% of, within less than or equal to 1 % of, within less than or equal to 0.1 % of, and within less than or equal to 0.01 % of the stated amount. The terms "about" and "substantially" may also be used herein with respect to measurable values and ranges due to expected variations known to those skilled in the art (e.g., limitations and variability in measurements).

[0049] Those skilled-in-the-art, in light of the present disclosure, will appreciate that many changes can be made in the specific embodiments which are disclosed herein and still obtain alike or similar result without departing from or exceeding the spirit or scope of the disclosure. One skilled in the art will further understand that any properties reported herein represent properties that are routinely measured and can be obtained by multiple different methods. The methods described herein represent one such method and other methods may be utilized without exceeding the scope of the present disclosure.

[0050] The foregoing description of various forms of the invention has been presented for purposes of illustration and description. It is not intended to beAttorney Docket No. 106191-171 exhaustive or to limit the invention to the precise forms disclosed. Numerous modifications or variations are possible in light of the above teachings. The forms discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

Attorney Docket No. 106191-171Claims1 . A magnetic assembly for use in a circulator application, the magnetic assembly comprising: a ferrite-based material having an elemental formula that identifies a number of formula units for each element in the formula; the elemental formula including both the elements of vanadium and aluminum with the number of formula units (x) for vanadium being less than or equal to 0.22 and the number of formula units (y) for aluminum being less than 0.60; and a dielectric material that surrounds at least a portion of the ferrite-based material; wherein the ferrite-based material and the dielectric material directly form a chemical bond there between.

2. The magnetic assembly according to claim 1 , wherein the formula units (x) for vanadium is in the range of 0.15 < x < 0.22.

3. The magnetic assembly according to any of claims 1 or 2, wherein the ferrite- based material corresponds to the following elemental formula and corresponding formula units:Y 3-z-2xCSz+2xF ©5-x-y-zAzV x Al y Ol 2 , with A being Ti, Zr, or Sn, wherein the formula unit (z) is given by 0 < z < 0.6 and the sum of the formula units (x) for vanadium and the formula units (y) for aluminum is in the range of 0.15 < x + y < 0.75.

4. The magnetic assembly according to any of claims 1 to 3, wherein the ferrite- based material is a yttrium iron garnet and the dielectric material is a magnesium calcium titanate-based ceramic.

5. The magnetic assembly according to any of claims 1 to 4, wherein the ferrite- based material has the following elemental formula and corresponding formula units:Y2.28Cao.72Fe4.23Zro.32Vo.20Alo.25O12-Attorney Docket No. 106191-1716. The magnetic assembly according to any of claims 1 to 5, wherein the ferrite- based material has a Curie temperature (Tc) that is > 155°C.

7. The magnetic assembly according to any of claims 1 to 6, wherein the ferrite- based material has a saturation magnetization (4TTMS) of at least 600 gauss.

8. The magnetic assembly according to any of claims 1 to 7, wherein the ferrite- based material includes a periphery that is circular in shape.

9. The magnetic assembly according to any of claims 1 to 8, wherein the ferrite- based material is a disk or a rod.

10. The magnetic assembly according to any of claims 1 to 9, wherein the dielectric material is shaped in the form of a ring.

11. The magnetic assembly according to any of claims 1 to 10, wherein the chemical bond between the ferrite-based material and the dielectric material is substantially free of any polymers, adhesives, or glues.

12. The magnetic assembly according to any of claims 1 to 11 , wherein the chemical bond between the ferrite-based material and the dielectric material reduces the susceptibility of the magnetic assembly to dielectric breakdown as compared to a similar magnetic assembly containing a similar ferrite material that comprises vanadium as an element and in which the formula units for an aluminum element is 0.00; the similar ferrite material having the same saturation magnetization as the ferrite-based material.

13. The magnetic assembly according to any of claims 1 to 12, wherein the ferrite- based material in the magnetic assembly has a Curie temperature (Tc) that is less than 20% lower than the Curie temperature of a similar ferrite material in a similar magnetic assembly that comprises vanadium as an element and in which the formula units for an aluminum element is 0.00; the similar ferrite material having the same saturation magnetization as the ferrite-based material.Attorney Docket No. 106191-17114. The magnetic assembly according to any of claims 1 to 13, wherein the chemical bond between the ferrite-based material and the dielectric material reduces the average leakage current of the magnetic assembly to less than 1 / 3 of the average leakage current exhibited by a similar magnetic assembly containing a similar ferrite material that comprises vanadium as an element and in which the formula units for an aluminum element is 0.00; the similar ferrite material having the same saturation magnetization as the ferrite-based material.

15. The magnetic assembly according to any of claims 1 to 15, wherein the chemical bond is formed by a thermally induced reaction occurring between the ferrite- based material and the dielectric material.

16. The magnetic assembly according to any of claims 1 to 15, wherein the ferrite- based material is a circular disk defined by a diameter ddisk; wherein the dielectric material is a ring defined by an inner diameter Din and an outer diameter Dout; wherein the inner diameter Din is smaller than the diameter Ddisk of the circular disk and the outer diameter Dout is equal to the diameter Ddisk of the circular disk.

17. The magnetic assembly according to any of claims 1 to 15, wherein the ferrite- based material is a rod defined by a diameter drOd and a height HrOd; wherein the dielectric material is a ring defined by a height King, an inner diameter Din and an outer diameter Dout; wherein the inner diameter Din is equal to the diameter DrOd of the rod and the outer diameter Dout is greater to the diameter DrOd of the rod; wherein the height HrOd of the rod is the same as the height Hringof the ring.Attorney Docket No. 106191-17118. A method for fabricating the magnetic assembly according to any of claims 1 to 17, the method comprising: providing a ferrite-based material in the form of a disk or a rod; providing a dielectric material in the form of a ring; placing a surface of the dielectric material in direct contact with a surface of the ferrite-based material; and co-firing the ferrite-based material and the dielectric material, thereby attaching the dielectric material to the ferrite-based material via a chemical bond.

19. The method according to claim 18, wherein the ferrite-based material and the dielectric material are co-fired at a temperature that is greater than 1 ,000°C.

20. The method according to any of claims 18 or 19, wherein providing the ferrite- based material comprises sintering the ferrite-based material to form the disk or rod.

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