What is claimed is:1. A magnetic storage device, comprising:a magnetoresistance effect element including:a storage layer having a variable magnetization direction,a reference layer having a fixed magnetization direction, anda tunnel barrier layer between the storage and reference layers in a first direction, whereinthe storage layer includes:a first layer that is magnetic and contacting the tunnel barrier layer,a second layer that is magnetic and farther from the tunnel barrier layer than is the first layer in the first direction, anda third layer between the first and second layers in the first direction and including a first portion that is an insulating material or a semiconductor material and a plurality of second portions that are conductive material and surrounded in a plane orthogonal to the first direction by the first portion, the plurality of second portions each extending in the first direction from the first layer to the second layer, whereinthe second layer is a cobalt/platinum artificial lattice layer, an alloy layer of cobalt and platinum, or an alloy layer of cobalt, platinum, and chromium.2. The magnetic storage device according to claim 1, wherein the third layer has a thickness of more than 1 nm but less than or equal to 5 nm.3. The magnetic storage device according to claim 1, wherein the second portions comprise at least one element selected from iron, cobalt, and nickel.4. The magnetic storage device according to claim 3, wherein the second portions further comprise at least one element selected from a lanthanide, aluminum (Al), silicon (Si), gallium (Ga), magnesium (Mg), tantalum (Ta), molybdenum (Mo), tungsten (W), calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), and hafnium (Hf).5. The magnetic storage device according to claim 1, wherein the first portion is formed of an oxide, a nitride, a boride, a II-VI semiconductor, or a III-V semiconductor.6. The magnetic storage device according to claim 5, whereinthe plurality of second portions comprise a magnetic metal,the first portion is an oxide, a nitride, or a boride, andan energy of formation of the oxide, nitride, or boride is less than an energy of formation of a corresponding oxide, nitride, or boride of the magnetic metal.7. The magnetic storage device according to claim 1, wherein the first portion is formed of an oxide having a spinel structure or an oxide having a corundum structure.8. The magnetic storage device according to claim 1, wherein the first layer comprises iron.9. The magnetic storage device according to claim 8, wherein the first layer further comprises cobalt and boron.10. The magnetic storage device according to claim 1, wherein perpendicular magnetic anisotropy of the second layer is higher than perpendicular magnetic anisotropy of the first layer.11. The magnetic storage device according to claim 1, wherein the first layer is magnetically coupled to the second layer via the third layer.12. The magnetic storage device according to claim 1, further comprising:a switching element connected to the magnetoresistance effect element in series.13. The magnetic storage device according to claim 1, whereinthe reference layer includes a plurality of cobalt-containing layers and a plurality of platinum-containing layers that are alternately stacked on each other.14. The magnetic storage device according to claim 1, further comprising:a cap layer on one of the storage or reference layers, andan under layer on the other of the storage or reference layers.15. The magnetic storage device according to claim 1, wherein a ratio of total area of the plurality of second portions to area of the third layer is within a range of 5% to 20%.16. A magnetic memory storage device, comprising:a plurality of first wirings extending along a first direction;a plurality of second wirings extending along a second direction crossing the first direction; anda plurality of memory cells extending along a third direction crossing the first and second directions between the first and second wirings, each of the memory cell including a magnetoresistance effect element that includes:a storage layer having a variable magnetization direction,a reference layer having a fixed magnetization direction, anda tunnel barrier layer between the storage and reference layers in the third direction, whereinthe storage layer includes:a first layer that is magnetic and contacting the tunnel barrier layer,a second layer that is magnetic and farther from the tunnel barrier layer than is the first layer in the third direction, anda third layer between the first and second layers in the third direction and including a first portion that is an insulating material or a semiconductor material and a plurality of second portions that are conductive material and surrounded in a plane orthogonal to the third direction by the first portion, the plurality of second portions each extending in the third direction from the first layer to the second layer, and the third layer has a thickness of more than 1 nm but less than or equal to 5 nm, whereinthe second layer is a cobalt/platinum artificial lattice layer, an alloy layer of cobalt platinum, or an alloy layer of cobalt, platinum, and chromium.17. The magnetic memory storage device according to claim 16, wherein each of the memory cells further includes a switching element connected to the corresponding magnetoresistance effect element in series.18. The magnetic memory storage device according to claim 17, wherein the switching element becomes conductive when a predetermined voltage is applied thereto through the corresponding first and second wirings.19. The magnetic memory storage device according to claim 16, wherein the reference layer is a cobalt/platinum artificial lattice layer.20. The magnetic memory storage device according to claim 16, wherein the reference layer is a cobalt-platinum alloy, an iron-platinum alloy, or an iron-cobalt-terbium alloy.