Aerosol-forming article containing magnetic particles

Abstract

To provide an improved aerosol-forming article and an electrically heated aerosol-generating device including a detector which offer additional functionality to a consumer, and increase difficulty in producing counterfeit articles.SOLUTION: The invention relates to an aerosol-forming article (10) for use in an electrically heated aerosol-generating device (30), the aerosol-forming article (10) including a mouthpiece (18), an aerosol-forming substrate (12), and a plurality of magnetic particles (22) including a magnetic material having a Curie temperature of 60°C-200°C. The invention also relates to the electrically heated aerosol-generating device (30) for receiving the aerosol-forming article (10), the device (30) including a heater element (32) to heat the aerosol-forming article (10), an inductor (38), and a controller (42) to measure an inductance of the inductor (38) and to control a supply of electrical current to the heater element (32) in response to the measured inductance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an aerosol-forming article for use in an electrically heated aerosol generation system, the aerosol-forming article comprising magnetic particles comprising a magnetic material having a Curie temperature of from about 60 °C to about 200 °C. The present invention also relates to an electrically heated aerosol generation device for receiving an aerosol-forming article, the device comprising an inductor and a heater element controlled in response to a measured inductance of the inductor. The present invention further relates to a method of operating the device in combination with an aerosol-forming article.

Background Art

[0002] Numerous documents, such as US-A-5 060 671, US-A-5 388 594, US-A-5 505 214, WO-A-2004 / 043175, EP-A-1 618 803, EP-A 1 736 065 and WO-A-2007 / 131449, disclose electrically operated aerosol generation, smoking, systems having a number of advantages. One advantage is that the sidestream smoke is significantly reduced while the smoker can selectively pause or resume smoking.

[0003] Electrically heated smoking systems generally comprise a power source (such as a battery) connected to a heater that heats an aerosol-forming substrate to form an aerosol provided to a smoker. In operation, these electrically heated smoking systems generally supply a high power pulse to the heater that provides a desired temperature range for operation to release volatile compounds. Electrically heated smoking systems may be reusable or may be arranged to receive a disposable smoking article comprising an aerosol-forming substrate to form an aerosol.

[0004] Aerosol generating, smoking articles developed for electrically heated smoking systems are generally specially designed because, without combustion as occurs in a cigarette with a lit end and other smoking articles, flavors are generated and released by controlled heating of an aerosol-forming substrate. Thus, the structure of a smoking article designed for an electrically heated smoking system can be different from that of a smoking article with a lit end. Using a smoking article with a lit end in combination with an electrically heated smoking system can result in a low-quality smoking experience for the user and can also damage the system, for example, because the smoking article is not compatible with the system. Further, there can be a number of different smoking articles, each configured to be used in combination with a system, that provide different smoking experiences for the user.

[0005] Some prior art electrically heated smoking systems include a detector capable of detecting the presence of a smoking article received in the smoking system. A generally well-known system prints a distinguishable ink on the surface of the smoking article, which is detected by the electrically heated smoking device. It is an object of the present invention to provide an improved aerosol-forming article and an electrically heated aerosol-generating device that include a detector to provide additional functionality to the consumer and make it difficult to manufacture counterfeits. SUMMARY OF THE INVENTION

[0006] Accordingly, the present invention provides an aerosol-forming article for use in an electrically heated aerosol-generating device, the aerosol-forming article including a mouthpiece, an aerosol-forming substrate, and a plurality of magnetic particles including a magnetic material having a Curie temperature of from about 60°C to about 200°C.

[0007] The term "aerosol-forming article" is used herein to mean an article that includes at least one substrate that forms an aerosol upon heating. As is well known to those skilled in the art, an aerosol is a suspension of solid particles or liquid droplets in a gas such as air. An aerosol can be a suspension of solid particles and liquid droplets in a gas such as air.

[0008] By providing a plurality of magnetic particles on or in an aerosol-forming article, the article formed according to the present invention advantageously provides a new means for an electrically heated aerosol-generating device to detect the presence of the article. In particular, in use, the aerosol-forming article is received within an electrically heated aerosol-generating device that includes means for detecting the presence of the magnetic particles. As will be discussed in more detail below, the means for detecting the presence of the magnetic particles preferably includes an inductor provided within the device.

[0009] Advantageously, by forming the magnetic particles from a magnetic material having a Curie temperature of from about 60 °C to about 200 °C, a further element can be added to the detection of the aerosol-forming article by the electrically heated aerosol-generating device. For example, the device can first detect the presence of the aerosol-forming article intended to be used in combination with the device by detecting the presence of the magnetic particles within the aerosol-forming article. After initial heating of the aerosol-forming article, the device can detect the temperature at which the properties of the magnetic particles change, which temperature indicates the Curie temperature of the magnetic material forming the magnetic particles. Based on the Curie temperature, the device can then perform further operations, such as introducing a specific heating profile depending on the type of the detected aerosol-forming article.

[0010] Thus, the magnetic particles preferably comprise a magnetic material having a Curie temperature that falls within the range of the operating temperature of the electric heater within the electrically heated aerosol-generating device. The magnetic particles can comprise a magnetic material having a Curie temperature of at least about 70 °C, preferably at least about 80 °C. Additionally or alternatively, the magnetic particles can comprise a magnetic material having a Curie temperature of less than about 140 °C, preferably less than about 130 °C.

[0011] The present invention preferably provides two or more types of magnetic particles for use in an aerosol-forming article, each type of magnetic particle having a different Curie temperature. In this way, a plurality of aerosol-forming articles can be provided, each having different types of magnetic particles such that the aerosol-generating device can distinguish the aerosol-forming article based on the detected Curie temperature and operate accordingly.

[0012] Furthermore, or alternatively, the present invention can provide a plurality of aerosol-forming articles, each containing a different amount of magnetic particles, such that the aerosol-generating device can distinguish different types of aerosol-forming articles based on the amount of magnetic particles and operate accordingly.

[0013] The magnetic particles can be incorporated into any component of the aerosol-forming article, including but not limited to paper (such as wrapper paper), filters, tipping paper, tobacco, tobacco wrap, coatings, binders, fixatives, adhesives, inks, foams, hollow acetate tubes, wraps, and lacquers. The magnetic particles can be incorporated into the components by any method, such as adding them to the paper slurry during the manufacture of the material, or attaching them before drying, or coating or spraying them onto the components.

[0014] In some embodiments, it may be preferable to provide the magnetic particles in the aerosol-forming substrate, particularly when used in combination with an electrically heated aerosol-generating device comprising a heater and an inductor inserted into the aerosol-forming substrate during use. Also, providing the magnetic particles within the aerosol-forming substrate prevents the particles from being released during subsequent handling of the aerosol-forming article during manufacture and during handling by the consumer.

[0015] It is preferred that the magnetic particles be distributed throughout the aerosol-forming substrate so that the orientation of the aerosol-forming article within the aerosol-generating device is not critical. This makes the use of the system easier for the consumer. In a particularly preferred embodiment, the magnetic particles are substantially uniformly distributed throughout the aerosol-forming substrate.

[0016] The magnetic particles are preferably present in an amount of from about 1 to about 30 weight percent, more preferably from about 1 to about 10 weight percent, and most preferably from about 1 to about 5 weight percent of the aerosol-forming substrate. Providing magnetic particles in these amounts ensures that there are sufficient numbers for effective detection by an electrically heated aerosol-generating device during use.

[0017] The number average diameter of the magnetic particles is preferably from about 25 micrometers to about 75 micrometers. This particle size range allows for the introduction of the magnetic particles into the aerosol-forming article with minimal modification to existing manufacturing processes. For example, in an embodiment where the aerosol-forming substrate comprises tobacco wrapped in cigarette paper, the magnetic particles can be added to and mixed with the tobacco during the conditioning / treatment of the tobacco before it is wrapped and formed into individual aerosol-forming articles. In an embodiment where the aerosol-forming substrate comprises tobacco in the form of a cast leaf sheet, magnetic particles having a diameter of less than about 75 micrometers can be incorporated into the cast leaf sheet without the need to increase the typical thickness of such sheets. Using magnetic particles having a diameter of at least about 25 micrometers can prevent the magnetic articles from moving from the aerosol-forming substrate to other parts of the aerosol-forming article or to the consumer during use of the article.

[0018] Suitable magnetic materials for forming the magnetic particles include ferrites, alloy iron, and nickel alloys.

[0019] The aerosol-forming article may comprise an aerosol-forming substrate, a hollow tubular element, an aerosol cooling element and a mouthpiece, which are arranged coaxially in sequence and surrounded by an outer wrapper. When the aerosol-forming article includes an outer wrapper, the outer wrapper can be, for example, the outer wrapper of cigarette paper.

[0020] The length of the aerosol-forming article can be from about 30 mm to about 120 mm, for example about 45 mm. The diameter of the aerosol-forming article can be from about 4 mm to about 15 mm, for example about 7.2 mm. The length of the aerosol-forming substrate can be from about 3 mm to about 30 mm.

[0021] As described above, the aerosol-forming article includes an aerosol-forming substrate. The aerosol-forming substrate preferably contains a tobacco-containing material that includes volatile tobacco flavor compounds released from the substrate upon heating. Alternatively, the aerosol-forming substrate can contain a non-tobacco material, such as those used in the devices of EP-A-1 750 788 and EP-A-1 439 876. The aerosol-forming substrate preferably further includes an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol. Additional examples of potentially suitable aerosol formers are described in EP-A-0 277 519 and US-A-5 396 911. The aerosol-forming substrate can be a solid substrate. The solid substrate can include one or more of, for example, powder, granule, pellet, fragment, spaghetti, flake or sheet, which includes one or more of herb leaves, tobacco leaves, fragments of tobacco stems, reconstituted tobacco, homogenized tobacco, extruded tobacco and expanded tobacco. Optionally, the substrate can contain additional tobacco or non-tobacco volatile flavor compounds released upon heating of the substrate.

[0022] Optionally, the solid substrate may be provided on or embedded within a thermally stable carrier. The carrier may take the form of, for example, powders, granules, pellets, fragments, spaghetti, chips or sheets. Alternatively, the carrier may be a tubular carrier having a thin layer of solid substrate disposed on its inner surface (such as those disclosed in US-A-5 505 214, US-A-5 591 368 and US-A-5 388 594), or on its outer surface, or on both its inner and outer surfaces. Such tubular carriers may be formed, for example, of paper, or paper-like materials, non-woven carbon fiber mats, low mass and coarse mesh metal screens, or perforated metal foils or any other thermally stable polymeric matrix. The solid substrate may be deposited, for example, in the form of a sheet, foam, gel or slurry on the surface of the carrier. The solid substrate may be deposited over the entire surface of the carrier or, alternatively, in a pattern to provide non-uniform flavor delivery during use. Alternatively, the carrier may be a non-woven fiber or bundle of fibers incorporating tobacco components, such as those described in EP-A-0 857 431. The non-woven fiber or bundle of fibers may include, for example, carbon fibers, natural cellulose fibers, or cellulose derivative fibers.

[0023] The aerosol-forming substrate may be a liquid substrate, and the smoking article may include means for holding the liquid substrate. For example, the smoking article may include a container such as that described in EP-A-0 893 071. As another or further alternative, the smoking article may include a porous carrier material into which the liquid substrate can be absorbed as described in WO-A-2007 / 024130, WO-A-2007 / 066374, EP-A-1 736 062, WO-A-2007 / 131449 and WO-A-2007 / 131450. The aerosol-forming substrate may alternatively be any other type of substrate (e.g., a gas substrate), or any combination of various substrate types. The magnetic particles may be incorporated into means for holding the liquid substrate, such as within the material forming a container for holding the liquid substrate. As another or additional alternative, where present, the magnetic particles may be incorporated into the porous carrier material.

[0024] The aerosol-forming article is preferably a smoking article.

[0025] According to a further aspect, the present invention provides an electrically heated aerosol-generating device for receiving an aerosol-forming article comprising a magnetic material, the device comprising a heater element for heating the aerosol-forming article and an inductor. The device further comprises a controller for measuring the inductance of the inductor and controlling the supply of current to the heater element in response to the measured inductance.

[0026] Advantageously, the aerosol-generating device according to the present invention can detect the presence of the magnetic material within the aerosol-forming article inserted into the device and accordingly control the current to the heater element. In particular, by detecting a change in the inductance of the inductor as a result of the magnetic material within the aerosol-forming article being positioned in the vicinity of the inductor, the controller can determine whether an aerosol-forming article intended for use in combination with the device has been inserted.

[0027] The control of the current to the heater element can include turning the current on, turning the current off, and adjusting the current supply in other ways. For example, when the presence of a magnetic material, such as magnetic particles in the aerosol-forming article described above, is detected, the controller can activate the supply of current to the heater element to initiate heating of the aerosol-forming article.

[0028] As described above, the controller can be configured to detect different types of aerosol-forming articles. For example, based on the inductance of the inductor measured when the aerosol-forming article is inserted, the controller can determine the amount of magnetic material present and accordingly determine the type of aerosol-forming article.

[0029] Furthermore, or alternatively, by repeatedly measuring the inductance of the inductor during heating of the aerosol-forming article, the controller can determine the temperature at which a significant change in inductance occurs, which temperature indicates the Curie temperature of the magnetic material within the aerosol-forming article. Based on the determined Curie temperature, the controller can determine the type of aerosol-forming article.

[0030] In response to determining the type of aerosol-forming article, the controller can accordingly adjust the supply of current to the heater element. For example, based on the type of aerosol-forming article, the controller can adjust the current to provide a specific heating profile appropriate for the type of aerosol-forming article.

[0031] The heater element preferably includes an electrically resistive material. Suitable electrically resistive materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composite materials made of ceramic materials and metal materials. Such composite materials may include doped ceramics or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable alloys include alloys containing stainless steel, nickel-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron, and nickel, iron, cobalt, stainless steel-based superalloys, Timetal® and iron-manganese-aluminum-based alloys. In composite materials, the electrically resistive material may optionally be embedded, encapsulated, or coated with a thermal insulation material, or vice versa, depending on the kinetics of the required energy transfer and the external physico-chemical properties. Examples of suitable compound heater elements are disclosed in US Pat. No. 5,498,855, WO 03 / 095688, and US Pat. No. 5,514,630.

[0032] The heater element can take any suitable form. For example, at least one heater element can take the form of a heating blade, such as those described in US-A-5 388 594, US-A-5 591 368 and US-A-5 505 214. Alternatively, at least one heater element may take the form of a casing or substrate with different conductive parts as described in EP-A-1 128 741 or with an electrically resistive metal tube as described in WO-A-2007 / 066374. As another alternative, one or more heating needles or rods passing through the center of the aerosol-forming substrate, as described in KR-A-100636287 and JP-A-2006320286, may also be suitable. Alternatively, at least one heater element may be a disc-shaped (end) heater or a combination of a disc-shaped heater and a heating needle or rod. Other alternatives include heating wires or filaments, such as those described in EP-A-1 736 065, for example wires or heating plates made of nickel-chromium (Ni-Cr), platinum, tungsten or alloys.

[0033] The heater element may heat the aerosol-forming article by conduction. The heater element may at least partially contact the aerosol-forming substrate or a carrier to which the substrate is attached. Alternatively, heat from the heater element may be conducted to the substrate by means of a thermally conductive element. As another alternative, the heater element may transfer heat to the ambient air drawn through the electrically heated aerosol generator during use, which in turn heats the aerosol-forming article by convection. The ambient air may be heated before passing through the aerosol-forming substrate, as described in WO-A-2007 / 066374.

[0034] The inductor may comprise a conductive coil connected to a controller such that the controller can measure the inductance of the inductor. The inductor is preferably arranged within the device such that when the article is inserted into the device, a magnetic material in the aerosol-forming article is located in the vicinity of the inductor.

[0035] The device preferably comprises a conductive coil that functions as both a heater element and an inductor. For example, the device may comprise a heater blade that includes a conductive coil embedded in a non-conductive substrate, where the conductive coil functions as an inductor and a resistive heater. Forming the heater element and the inductor from a single conductive coil is cost-effective and simplifies the manufacture and construction of the device.

[0036] In an embodiment where the device comprises a single conductive coil that functions as both a heater element and a conductor, the controller is preferably configured to pulsate the supply of current through the conductive coil to heat the aerosol-forming article and measure the inductance of the conductive coil between current pulses. The controller may be configured to pulsate the supply of current through the conductive coil at a frequency of from about 1 MHz to about 30 MHz, preferably from about 1 MHz to about 10 MHz, more preferably from about 5 MHz to about 7 MHz.

[0037] According to a further aspect, the present invention provides an electrically heated aerosol generating system comprising a combination of an electrically heated aerosol generating device according to any of the above embodiments and an aerosol-forming article according to any of the above embodiments.

[0038] According to a further aspect, the present invention provides a method of operating an electrically heated aerosol generating system, the system comprising an aerosol forming article, a heater element for heating the aerosol forming article, an inductor, and a controller configured to measure an inductance of the inductor and control the supply of current to the heater element. The method includes measuring the inductance of the inductor and comparing the measured inductance with one or more predetermined inductance values. The supply of current to the heater element is controlled based on a comparison between the measured inductance and the one or more predetermined inductance values.

[0039] For example, if the measured inductance does not correspond to a reference inductance, the controller may assume that either the aerosol forming article is not present in the device or the inserted aerosol forming article does not contain a magnetic material and is therefore not designed to be used in combination with the device. Under these circumstances, the controller may be configured to prevent the supply of current to the heater element. That is, the controller does not activate the heater element. Thus, the step of controlling the supply of current to the heater element preferably includes not supplying current to the heater element if the measured inductance does not match any of the one or more predetermined inductance values, where the one or more predetermined inductance values each correspond to a type of aerosol forming article designed to be used in combination with the device.

[0040] Alternatively, if the measured inductance is significantly different from a reference inductance, the controller may assume that an aerosol forming article designed to be used in combination with the device has been inserted. In this case, the controller may turn on the supply of current to the heater element and initiate heating of the aerosol forming article.

[0041] When the device can be used in combination with different types of aerosol - forming articles, one or more predetermined inductance values may include a plurality of predetermined inductance values, where each predetermined inductance value corresponds to the type of aerosol - forming article. In this case, the step of controlling the supply of current to the heater element may include the step of varying the current supplied to the heater element to provide a predetermined heating profile, where the predetermined heating profile is selected based on which of the plurality of predetermined inductance values matches the measured inductance. That is, the appropriate heating profile is selected for the type of aerosol - forming article inserted into the device. For example, different types of aerosol - forming articles may contain different amounts of magnetic material, such as different amounts of magnetic particles as described above. In this case, each of the predetermined inductance values corresponds to the inductance of the inductor when located in the vicinity of the corresponding amount of magnetic material.

[0042] Furthermore, or alternatively, the device may be designed to function with different types of aerosol - forming articles containing magnetic materials having different Curie temperatures, such as different types of magnetic particles as described above. In such embodiments, the step of controlling the supply of current to the heater element includes the step of activating the supply of current to the heater element to heat the aerosol - forming article to a temperature above the Curie temperature of the plurality of magnetic particles. In this case, the method further includes the steps of repeatedly measuring the inductance of the inductor and the temperature of the heater element during heating of the aerosol - forming article, and determining when a decrease in the inductance measured during heating of the aerosol - forming article occurs, where this decrease in inductance indicates that a plurality of magnetic particles have been heated to their Curie temperature. The current supplied to the heater element is then varied to provide a predetermined heating profile, where the predetermined heating profile is selected based on at least one of the time at which the measured decrease in inductance occurs and the heater - element temperature at which the measured decrease in inductance occurs.

[0043] As described above, the electrically heated aerosol generator may comprise a conductive coil that forms both the heater element and the inductor. In this case, the step of starting the supply of current to the heater element to heat the aerosol-forming substrate includes the step of pulsing the supply of current through the conductive coil, and the step of repeatedly measuring the inductance of the inductor includes the step of measuring the inductance of the conductive coil between current pulses. The step of pulsing the supply of current through the conductive coil may include pulsing the supply of current through the conductive coil at a frequency of from about 1 MHz to about 30 MHz, preferably from about 1 MHz to about 10 MHz, more preferably from about 5 MHz to about 7 MHz.

[0044] Hereinafter, the present invention will be further described with reference to the following attached drawings, which are for illustrative purposes only.

Brief Description of the Drawings

[0045]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0046] Figure 1 shows an aerosol-forming article 10 comprising an aerosol-forming substrate 12, a hollow acetate tube 14, a polymeric filter 16, a mouthpiece 18, and an outer wrapper 20. The aerosol-forming substrate 12 includes a plurality of ferromagnetic particles 22 distributed within a plug of tobacco 24. The mouthpiece 18 includes a plug of cellulose acetate fibers.

[0047] Figure 2 shows an aerosol - forming article 10 inserted within an electrically - heated aerosol - generating device 30. The device 30 includes a heater element 32 having a base portion 34 and a heater blade 36 that passes through the aerosol - forming substrate 12. The heater blade 36 includes a conductive coil 38 configured to receive a supply of current from a battery 40 provided within the device 30. A controller 42 controls the operation of the device 30, including the supply of current from the battery 40 to the conductive coil 38 of the heater blade 36.

[0048] During use, the controller 42 determines that the aerosol - forming article 10 is suitable for use in combination with the device 30 by detecting a change in the inductance of the conductive coil 38 as a result of the ferromagnetic particles 22 within the aerosol - forming substrate 12 being located in the vicinity of the conductive coil 38.

[0049] After determining that the aerosol - forming article 10 can be used in combination with the device 30, the controller 42 pulsates the current passed through the conductive coil 38 from the battery 40 and starts heating the aerosol - forming substrate 12. Between pulses of the current, the controller 42 continues to monitor the inductance of the conductive coil 38 and determines the point at which a significant change in inductance occurs. The change in inductance indicates that the ferromagnetic particles 22 have been heated to their Curie temperature. The controller determines the temperature by measuring the resistivity of the conductive coil 38 at the instant the inductance changes. Based on the Curie temperature, the controller 42 determines the type of the aerosol - forming article 10 and selects an appropriate heating profile.

Claims

**Claim 1** An aerosol-forming article for use in an electrically heated aerosol-generating device, the aerosol-forming article comprising a mouthpiece, an aerosol-forming substrate, a plurality of magnetic particles comprising a magnetic material having a Curie temperature in the range of 60 °C to 200 °C, the plurality of magnetic particles comprising a magnetic material having a Curie temperature falling within the range of the operating temperature of an electric heater within the electrically heated aerosol-generating device, and wherein the aerosol-forming article comprises an outer wrapper having a plurality of magnetic particles provided therein, or a filter having a plurality of magnetic particles provided therein, the aerosol-forming article. **Claim 2** The aerosol-forming article according to claim 1, wherein the number average diameter of the magnetic particles is from 25 micrometers to 75 micrometers. **Claim 3** The aerosol-forming article according to claim 1 or 2, wherein the aerosol-forming substrate comprises tobacco in the form of a cast leaf sheet. **Claim 4** The aerosol-forming article according to any one of claims 1 to 3, wherein the plurality of magnetic particles comprises a magnetic material having a Curie temperature of at least about 70 °C. **Claim 5** The aerosol-forming article according to any one of claims 1 to 4, wherein the plurality of magnetic particles comprises a magnetic material having a Curie temperature lower than about 140 °C. **Claim 6** The aerosol-forming article according to any one of claims 1 to 5, wherein the length of the aerosol-forming article is from about 30 mm to about 120 mm. **Claim 7** The aerosol-forming article according to any one of claims 1 to 6, wherein the diameter of the aerosol-forming article is from about 4 mm to about 15 mm. **Claim 8** A plurality of aerosol-forming articles according to any one of claims 1 to 7 for use in an electrically heated aerosol-generating device comprising a heater element for heating the aerosol-forming article, an inductor, and a controller configured to repeatedly measure the inductance of the inductor and the temperature of the heater element and to vary the supply of current to the heater element in response to the measured inductance to provide a predetermined heating profile, wherein the aerosol-forming article is configured such that the plurality of magnetic particles are in the vicinity of the inductor when the aerosol-forming article is used in the electrically heated aerosol-generating device and is heated by the heater element. **Claim 9** A plurality of aerosol-forming articles for use in an electrically heated aerosol-generating device, each aerosol-forming article being as claimed in any one of claims 1 to 7. **Claim 10** The plurality of aerosol-forming articles according to claim 9, each aerosol-forming article containing a different amount of magnetic particles.

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